> First one of the users got an error doing something with my application.

I think Vlads question (what errors did you get?) would be best answered by describing 'something' and telling which error message Firebird produced (that is, the error the Firebird engine reports, which may be different from what your program reports to your user).

> What do you mean saying "wrong usage of gfix". The first thing I did was to do gfix -mend. Was this wrong?

I think Vlad is saying that CORE-2268 is an error only relating to gfix, and that this particular error is not the same error as the one you observe (CORE-2268 occurs when you try to use gfix to commit a specific transaction that doesn't exist, and you haven't said anything about your problems starting after using 'gfix -commit <non-existing transaction number>').

HTH,
Set