Comment on Debian Squeeze/Sid Unstable Compiz fix Gnome Run Application Alt+F2 problem by jmcnaught.
Hello,
This post helped me figure out how to fix this same problem, and it was a little easier so I thought I’d share it.
I also went into the CompizConfig Settings Manager, and right beside the “General Options” there was a “Gnome Compatibility” plugin that was disabled. Enable that plugin by adding a check-mark beside it and you will get Alt-F2 and a few other things working again.
You may or may not need the compiz-gnome package (it was already installed for me).
jmcnaught