Timers interfere with code. If your application uses them, it is imperative that you code yourself a way to turn them all off when you are developing. Obviously, you need them on for testing but I have my start up form prompt me (by checking who logged in) so I don't forget to turn them off. The login form automatically turns them back on when it closes so I don't forget to do it.
I also have code that raises an error message if it is NOT me and the timers are NOT enabled and then refuses to open the database.