Mine runs the 880 firmware, and it's temps usually vary between 47 and 50 C, depending on ambient. I would say you could go higher than 800.

The auto tune works by loading the fastest firmware, and running it for a set amount of time (I think 20 minutes?). If it throttles at all in that time, then it drops to the next lowest firmware. It keeps repeating this process until it finds a firmware slow enough that the unit doesn't throttle.

Did the auto-tune decide on the 800 firmware? I would try manually loading some other firmware, like the 880 or the 864.

Maybe, if you can add an additional fan or two to keep it cool

You could try older versions, perhaps one works, which would allow to transfer stored funds to a new wallet?
Sorry, I guess some of the core devs could perhaps give some more help here.

Dia

Did you try -salvagewallet (command-line option, which moves any existing wallet.dat
  to wallet.{timestamp}.dat and then attempts to salvage public/private
  keys and master encryption keys (if the wallet is encrypted) into
  a new wallet.dat. This should only be used if your wallet becomes
  corrupted, and is not intended to replace regular wallet backups.)?

Make a backup of your wallet.dat before anyway!

Dia

When they tell me my SC Single is ready. 

Ya I had to give it some TLC, but I like tinkering. The fan direct is actually standard, as I guess it works better blowing up if you leave it in it's case, but works better blowing down if you take it out of it's case. Either way, it's pretty easy to take out of it's case.

The thermal paste is another issue, as some people have said that theirs were fine, others havn't had as much luck. I do think mine was a random occurrence, tho.

And finally, BFL doesn't care if you take it apart or open it up or repaste it or whatever. As long as you don't break it, they'll still accept it as an upgrade. I still plan on putting it back together when I do send it in, of course.

Just plug it in and run cgminer.  If it starts throttling, then worry about changing the bitstream.  Most of the time when I tried autotuning, it installed a bitstream that was too fast and ended up throttling, leading me to manually lower the bitstream back to normal anyway.

I got mine, plugged it in, and it was throttling even with the stock 832 firmware. I had to bump it down to the 816 firmware so it wouldn't throttle.

Then I took it apart, repasted  the chips with some CM stuff (they used WAY too much paste), directed the fan down instead of up, attatched a small 80mm CPU fan from and old AMD heatsink, and now I run it outside of it's case and laying on it's side. The Easyminer autotune flashed it with the 880 firmware, which is what I'm running now. I could prolly switch to the 896 since I added the extra fan on the bottom, but I havn't done it yet.

Using CGMiner, and it's been great.

AutoTune loads bfl firmware from the fastest downwards, until your unit stops throttling.

go here:

http://www.butterflylabs.com/drivers/

and get this:

http://www.butterflylabs.com/wp-content/uploads/2012/05/EasyMiner_V1.2_Beta.exe

and this:

http://www.butterflylabs.com/wp-content/uploads/2012/05/AutoTunePackage_Single.bfp

Then use EasyMiner, run AutoTune, and select the AutoTune package file when prompted.

Can you pastebin your debug.log?

You can also try the newly introduced (0.7.1):

Dia

Errors accessing wallet.dat as described above are likely from bitcoin (in one form or another) still running. Alternately, the wallet file could have been corrupted by attempting to run two different versions of Bitcoin which may concurrently access the same data directory.

Bitcoin takes a considerable amount of time to shut down after you tell it to. Bitcoin-qt (the full GUI version) will "close" when you press the close button, but it may still run in the background for a minute as it shuts down and closes the database files. Bitcoind (the daemon) may be running in a console window, but it doesn't need a window showing on your current desktop to be running.

In Ubuntu, press the superkey (Windows key), and type "System Monitor" and launch it. In the system monitor, check the processes tab to see if any copy or version of Bitcoin is running. If so you must close it and allow it to finish closing.

You do not state what version you are using or where you got it from. Either run bitcoin-qt extracted from the Sourceforge Bitcoin release bitcoin-0.7.1-linux.tar.gz (bitcoin.org -> Linux version), or follow these instructions:

Ubuntu Linux users can use the "Personal Package Archive" (PPA) maintained by Matt Corallo to automatically keep up-to-date. Just type:
sudo apt-add-repository ppa:bitcoin/bitcoin
sudo apt-get update

in your terminal, then install the bitcoin-qt package:
sudo apt-get install bitcoin-qt

You should first remove any bitcoind or older version you have installed. Additionally, if you have never used your wallet or the addresses in it, a good fresh start would be to remove the .bitcoin directory in your home directory, which is where all data files for Bitcoin are stored.

After installing the newest version, it can be launched by typing bitcoin-qt in a terminal window if it is not added to your menu bar. Then let it run for the day or two it requires to download 4GB of data.

I did not say "lost".

From what you wrote, it seems that the bitcoin-client has
difficulties to open and use your wallet. Most likely the
information is still stored in it, but you may have to do
some sorcery to get the client use it.  The much easier
way, of course, is when you have a backup.

I'm not a developer of any bitcoin-client.

What's current state of affairs?  Do you have a backup?
What order of value was stored in it? (i.e.: does it even
pay to spend effort on recovering it?)

You *do* have a backup, don't you?  Terminate all running clients, restore from backup and restart...

Don't have one? And more than just a few peanuts of btc in the wallet? Probably not all hope is lost,
but prepare for a bumpy road ahead.