Navigate to console and type:
walletpassphrase
dumprivkey
Copy a private key, remove all files in ./appdata/roaming/q2c, and run qt app. It creates a wallet.dat with new public/private keys.
Set tax per transaction to 0.001Q2C, then navigate to console and type:
importprivkey
It imports private key from old wallet and rescans all transactions.
OMG, it's even worse now!
I lost many other blocks after entering these commands. Now i don't missing only 12 000 but 88 000 Q2C! Now there are no coins from 8th march and from few other days too.
Please, help me devs!
Do you have a backup of your old wallet (.dat file)? Maybe you should try restoring that wallet.
Check into your wallet whether all addresses are listed there. Do you miss some addresses?
Regarding your initial problem, you probably were out of sync or you mined some orphaned blocks.
But what will be with my coins in new wallet? Should i send all to old account before this? (i have a backup of wallet.dat). I don't want risk to loose all. And I never used that address function of wallet, it's useless for me.
20 out of sync blocks or orphans in a row? I don't think it is possible.