Today I've got this error few times when my application executes a stored procedure with simple INSERT RETURNING statement inside.

And this is happened today on 3 separate databases on 3 different computers. I'm executing the procedure with SYSDBA user.

Restarting of the application fixes the problem, but still I'm wondering what cause this kind of error. And is it dangerous?

Firebird 2.1.3
Windows XP SP3