Disable "a program is still running" dialog in gnome

[Raj Kiran Grandhi <grajkiran@gmail.com>]

Nowadays, when I try to shutdown my system, I sometimes get this 
unhelpful dialog:

http://imgur.com/tRv5S.png

It complains about an unknown program that is not responding and wants 
to give me the "option" of waiting for it to finish. Is there any way to 
disable this dialog permanently? More than once I have left my machine 
thinking it would have shutdown only to find this annoying dialog a 
couple of hours later.

Thanks,
Raj Kiran