Currently all my label assignments in Opera Mail are lost.

This is how it happened:

1. Yesterday i had a power blackout on my PC while Opera Mail was opened (but not used at the moment).
2. After power was back, i restarted the PC and tried to start Opera Mail but got an error message telling me that there's something wrong with the database and i should restart the PC. 
3. After restarting the PC another time, Opera Mail opened but all label assignments are lost!

For me, this is really a disaster as i use Opera Mail for my business communication and i had dozens of well configured labels that were very important for me.

Is there any chance to get the label assignment back?

Some additional information:
I have a mail backup from 25.November.
"indexer.aax" file size of backup is 8 MB
"indexer.aax" file of current Opera Mail installation is only 96 kB!

Is it possible to restore just the indexer.aax file so that i get my labels back without loosing new mails?