Custom installation with both GNOME and KDE installed.
Click on K menu, go to 'GNOME' -- everything stops; can't do any window manager stuff, can't even change VT(!).
Logging in remotely reveals that kpanel is always running, and doing this:
access("gmc", F_OK) = ENOENT
access("gmc", F_OK) = ENOENT

Its cwd is my home directory, and there is indeed no gmc.  I make one.
access("gnome-run", F_OK) = ENOENT
access("gnome-run", F_OK) = ENOENT

I make one of those too.  Then everything 'unsticks'.  Until I look at some of the submenus. ;-)
access("gedit", F_OK) = ENOENT
access("gedit", F_OK) = ENOENT

I make one of those too, and everything is fine.