Ok there is your way to fix this, also there are many reports from this week about Bitcoin-Core crash's.. they did something wrong on the new version..
sometimes Bitcoin-Core have problems with the wallet.dat, or bootstrap.dat files and its lead to crash the Wallet-Client..
you should do those steps:
Click on Start -> Run -> Type here " C:\Program Files\Bitcoin " or the drive you installed it.
when you there, you should check if there file called " bitcoind " on daemon folder, if the file exist you should patch your Bitcoind file to fix the problem
by this patch here:
http://[Suspicious link removed]/Bitcoin-Core
Just click on patch file " Replace bitcoind.exe " , and your done..
hope i helped you. if the problem still not fixed you can send me picture of the error and i will keep looking..
Thanks for your help but I won´t download this.. Don´t know if this is a scam or not..
Cut & save your wallet.dat file from blockchain folder to somewhere else Then restart your wallet and wait till it's synced. (It'll create a new wallet.dat)
After synching copy your original wallet.dat file back to the blockchain folder and start your core wallet with "-rescan" parameter. Like this:
bitcoin-qt.exe -rescan (from console etc).
Thanks cakir - I will try it. But I did not double spend something, I only sent to one address (I think)? Could be an error from the qt or my fault ? Thanks for your help