An explanation and solution is here: http://forums.linuxmint.com/viewtopic.php?f=198&t=67502&p=510197#p512994
SOLUTION
--------------
My version of the solution above is a follows:
1. First, locate the file to edit
locate utils.js | grep misc
which returns
/usr/share/gnome-shell/js/misc/util.js
2. Next, confirm that argc is present (this is what's causing the problems)
cat /usr/share/gnome-shell/js/misc/util.js | grep argc
which returns
let [success, argc, argv] = GLib.shell_parse_argv(command_line);
let success, argc, argv;
[success, argc, argv] = GLib.shell_parse_argv(command_line);
There are more elegant ways of doing this, but this is how I roll.
3. Edit /usr/share/gnome-shell/js/misc/util.js as root
sudo vim /usr/share/gnome-shell/js/misc/util.js (you can of course use gedit, nano, emacs etc.)
search for argc and remove all instances of of it, so that
[success, argc, argv] turns into to [success, argv]
etc.
Once you've removed all argc, save and then hit alt+f2 in gnome, type r and enter to restart the shell. Then hit alt+f2 and type e.g. gedit to test it
It now works!
Reading through bug reports it seems it won't be fixed in Debian -- instead we'll have to wait until gnome 3.2 rolls out. Or just follow the instructions above.
-------------------------------
THE OLD POST
20/12/2011
(Current version of gnome-shell is 3.0.2-8+b1)
Hitting alt+f2 to start e.g. gedit or another program used to be straightforward.
During the past week it hasn't worked properly though -- instead the entry of any command has returned a 'command not found'. If you instead of simply typing in gedit type in /usr/bin/gedit, chances are the computer will experience an odd sort of freeze -- the top bar will be unresponsive, the black entry box will remain, the screen will be shaded, but gedit won't open. You will, however, be able to continue using your computer, but it'll be a dark experience.
Symptomatic descriptions of the bug and experiences are available here:
https://bugzilla.redhat.com/show_bug.cgi?id=719675
https://bugs.launchpad.net/ubuntu/+source/gnome-shell/+bug/816762
