input method doesn't work sometimes
 

I'm using Sarge with Gnome 2.8. X Input Method is set to be the
default input method. But sometimes it stops working, that means
pressing any of the keys on the keyboard doesn't give me the
corresponding letter in the input box. I have to change the input
method of that certain input box to "Default" in order to keying any
letters. This happens to Gaim most of the time, but IIRC it had
happened once to Firefox. Is it a problem with Debian?