Is there support for Firebird?
If you want free support from community, visit firebird-support mailing list at yahoogroups.com. It's one of the best organized and maintained support lists for any piece of software you used. Many of the people replying to messages are long time users of InterBase and Firebird, and some even the developers. Replies are quick and accurate and solve 99% of the problems that show up.
You can purchase support from IBPhoenix. While the name doesn't seem to be related with Firebird, you should know that many IBPhoenix employees are contributors to the project and IBPhoenix is one of main sponsors of Firebird development. Experts at IBPhoenix have a long time experience and deep knowledge of Firebird and InterBase internals, so there probably isn't a problem they can't solve.
If you have problems with corrupt databases, you can also contact IBSurgeon, who also have tools to detect problems and even fix some automatically. If all else fails, you can always send the database (under NDA) for analysis. In any case, it's best to make regular backups following the old rule: you should back up as much data as you cannot afford to lose.