Bitcoin-QT not loading

[BillyM]

I installed Bitcoin-QT last summer and made a few transactions with no problems.  I tried to load it up again yesterday, for the first time since October, and it did not load.  I get the flash screen but then it fails almost immediately when it is still on the first step "Verifying database integrity" and I get a Windows error message saying "Bitcoin-qt.exe has stopped working". 

I had 0.7.0 installed (I think), so I tried getting the latest version (0.7.2) and installed it without difficulty, but I get the exact same problem trying to load it up.  I have tried disabling my firewall but that didn't help.  Can anyone help me with some suggestions on how to fix this?  I am using Windows 7.

As an attempted workaround, I installed Multibit, which loads fine.  I expected to be able to load my wallet.dat file (which I have located and backed up) in Multibit, but Multibit only has the option to open a .wallet file, not my wallet.dat file.  Can anyone explain what I am missing here?

TIA

[Gabi]

Can anyone explain what I am missing here?

Multibit does not ope bitcoin-qt wallets, but only multibits wallets. You have to export the private keys from qt and import them in multibit.

This said, multibit is a good client.

[BillyM]

Thanks Gabi, that makes sense.  Is that the same with other clients?  It sounds like the only way to retrieve the bitcoins that are at the addresses stored in my wallet.dat file is to get Bitcoin-QT working again.

Could it be some software compatibility issue?  It fails when "verifying database intergrity", but what database?  Could there be a corrupt file somewhere, but then how could there be if I just did a fresh install?

[Gabi]

It sounds like the only way to retrieve the bitcoins that are at the addresses stored in my wallet.dat file is to get Bitcoin-QT working again.

No, as i said if you export the private keys you can move them to another client. You can for example use blockchain.info webwallet, just drag and drop there wallet.dat (note: learn how blockchain.info works before doing this)

It fails when "verifying database intergrity", but what database?

The blockchain (note: do not confuse with the website blockchain.info  )that the qt client have to download.

I don't know why it doesn't work, sorry

[BillyM]

Thank you.  I really appreciate you helping me.

No, as i said if you export the private keys you can move them to another client. You can for example use blockchain.info webwallet, just drag and drop there wallet.dat (note: learn how blockchain.info works before doing this)

OK, I created a webwallet at blockchain.info, and I've found the import wallet page where it says you can import keys, but wallet.dat is not one of the formats it says you can import.  These are the formats it says:

    AES encrypted backup from blockchain.info. (Must be encrypted with the same password)
    Plaintext JSON backup from blockchain.info
    Output from pywallet.py -dumpwallet
    Output from Multibit .key
    Output from Vanitygen

I can see the area where it says "Copy and paste your wallet data into this area", but nothing happens when I drag my wallet.dat file into the area.  Does "your wallet data" mean something different to "your wallet.dat file"?

[Gabi]

No, you just have to drag it in the square https://blockchain.info/it/wallet/import-wallet

[BillyM]

OK, thanks, I got, it worked.  I thought I was supposed to create a new webwallet and then import the wallet.dat info into it, but you meant by dragging wallet.dat and dropping it into the box, it would become my webwallet.  My mistake.  Now I have two webwallets on blockchain.info, which seems pointless, maybe I'll delete one if I can figure out how to do so.

[DannyHamilton]

- snip -
Now I have two webwallets on blockchain.info, which seems pointless, maybe I'll delete one if I can figure out how to do so.

Just send all the coins from one wallet to an address at the other wallet.  Then never log into the empty wallet again.  No need to "delete" it.  You can just stop using it.

[BillyM]

Well the first one's empty, so that's no problem.  I'll just forget I even opened it.

[BillyM]

Hello again, I have another question or two.

When I used my wallet.dat to create a new webwallet on blockchain.info, it seemed to be incomplete.  The last transaction on it was from April and I was sure I had made transactions after this, and also I thought I had more receiving addresses.  So that was weird, like the file was not fully updated or something, but I thought maybe I was mistaken.

I decided to try installing QT on my laptop.  It all went OK and it started downloading the blocks.  An entire week later (!), they had all downloaded and it was in sync.  I overwrote the empty wallet.dat with my original wallet.dat.  And sure enough, there were my missing transactions, showing in QT!

So what I can't get my head round is why the webwallet version doesn't show as many transactions as QT.  Shouldn't a webwallet always be up-to-date?

Second question: in both versions of the wallet, it is showing me as receiving BTC to addresses that aren't listed as one of the receiving addresses in the address book.  How is that possible?

[DannyHamilton]

So what I can't get my head round is why the webwallet version doesn't show as many transactions as QT.  Shouldn't a webwallet always be up-to-date?

Yes.  I would expect the web wallet to be up to date.  Was the balance incorrect, or just the transaction list?

Second question: in both versions of the wallet, it is showing me as receiving BTC to addresses that aren't listed as one of the receiving addresses in the address book.  How is that possible?

With the way bitcoin works, you can't partially spend a previous output that you received.  It has to be completely spent.  So, if you receive 10 BTC all in a single transaction from someone/somewhere at an address, then that address now has a single 10 BTC output.

Later if you want to send 2 BTC to somebody, the program can use the previous 10 BTC output as an input into the transaction, and create a 2 BTC output to the address where you want to send it.  This leaves 8 BTC leftover in the transaction.  If you don't send those 8 BTC somewhere, then they become miner fees and end up in the coinbase transaction of the new block for the miner to keep.  If you don't want to give those 8 BTC away as fees to the miner, then you need to include a second output in your transaction sending the 8 BTC back to your own wallet.  As an analogy, think of pulling a $10 bill out of your pocket to pay for something that costs $2, you get $8 back in "change".

The way Bitcoin-Qt does this is to create a new bitcoin address that it doesn't tell you about and keep track of that address and the associated private key in your wallet.dat.  Since this isn't an address that you requested in the "Receive Coins" tab of the user interface, it doesn't show up in that list.  Bitcoin-Qt knows about the address since it is in the wallet.dat file, so it includes it in the balance that it shows you.  Bitcoin-Qt uses a new change address for every transaction.  So if you create 10 different transactions, each sending bitcoins somewhere, then your wallet will have used 10 different change addresses (although some of them may be empty if Bitcoin-Qt used the bitcoins associated with some of those address as inputs into other transactions).

[BillyM]

So what I can't get my head round is why the webwallet version doesn't show as many transactions as QT.  Shouldn't a webwallet always be up-to-date?

Yes.  I would expect the web wallet to be up to date.  Was the balance incorrect, or just the transaction list?

The balance was incorrect as well.

Second question: in both versions of the wallet, it is showing me as receiving BTC to addresses that aren't listed as one of the receiving addresses in the address book.  How is that possible?

With the way bitcoin works, you can't partially spend a previous output that you received.  It has to be completely spent.  So, if you receive 10 BTC all in a single transaction from someone/somewhere at an address, then that address now has a single 10 BTC output.

Later if you want to send 2 BTC to somebody, the program can use the previous 10 BTC output as an input into the transaction, and create a 2 BTC output to the address where you want to send it.  This leaves 8 BTC leftover in the transaction.  If you don't send those 8 BTC somewhere, then they become miner fees and end up in the coinbase transaction of the new block for the miner to keep.  If you don't want to give those 8 BTC away as fees to the miner, then you need to include a second output in your transaction sending the 8 BTC back to your own wallet.  As an analogy, think of pulling a $10 bill out of your pocket to pay for something that costs $2, you get $8 back in "change".

The way Bitcoin-Qt does this is to create a new bitcoin address that it doesn't tell you about and keep track of that address and the associated private key in your wallet.dat.  Since this isn't an address that you requested in the "Receive Coins" tab of the user interface, it doesn't show up in that list.  Bitcoin-Qt knows about the address since it is in the wallet.dat file, so it includes it in the balance that it shows you.  Bitcoin-Qt uses a new change address for every transaction.  So if you create 10 different transactions, each sending bitcoins somewhere, then your wallet will have used 10 different change addresses (although some of them may be empty if Bitcoin-Qt used the bitcoins associated with some of those address as inputs into other transactions).

OK, I think I get that.  But I received BTC to this non-showing address just 2 weeks ago, and I didn't send anyone any BTC at that time.  This BTC was sent to me by someone that I had sent the address to last year.  How was I able to generate this address if it was only one that gets used for "change" when sending BTC out, and never gets revealed to me?  I expect I probably created a new address just to send to this person, but then I would expect it to be in my address book.  Still confused!