… and the Super key. I don’t know if everybody knew about this trick already, but it seems that Gnome has got this bug, that doesn’t let you bind keyboard shortcuts with the Super (windows key) combination, except the Super key itself (alone). Anyways, the work-around is using the Gnome Configuration Editor and just type in the combination in text. Browse to /apps/metacity/ (there are 4-5 sections).
If you don’t have the gconf-editor just yum install it (in Fedora):
yum install gconf-editor