> How can i close my app without generate errors?

This should never be a problem. Is your database server on the same PC as
the desktop application? What operating system? Which version of Interbase?
What error message do you get?

When the database got corrupted, did you create a new one from scratch in
order to test it again? A possible cause for corruption is copying the
database to another location while Interbase is still working with it.

Cheers,
Tobias