Today, same error. :( I was in a hurry to make stuff working again, so
I just quickly restarted Firebird (no time for playing). But looking
into log, I see also:
Database:
I/O error for file "/fbsql/<filename>.fdb"
Error while trying to write to file
Bad file descriptor

The database isn't corrupted, gfix shows no error. It always happens
in day load. Never during night or weekend.

--
Jiri {x2} Cincura (CTO x2develop.com)
http://blog.vyvojar.cz/jirka/ | http://www.ID3renamer.com