I have a few customers still working on XP with Firebird 2.5.8 32 bit. And it seems that a problem is introduced in 2.5.7 or 2.5.8. In semi regular periods, the Firebird server hangs (hogs CPU). This reappears after a restart of the Firebird server and accessing the database again. Only solution is making a backup, without Garbage collection, and restore. I can deliver databases with the problem for reproduction.