I had the same problem as stated here: http://www.eternal-l...showtopic=57157, but the posted solution didn't work for me.
After extended googling I found an howto:
Open terminal (ctrl-alt-t)
install gconf-editor
Open gconf-editor
Expand: Apps
Expand: Metacity
Click on General
Find mouse_button_modifier
Click on value column at mouse_button_modifier line
Delete the <Alt>
Type <Super>
Press enter
Close gconf-editor
Now you are good to go.
Source: http://forums.fedora...ad.php?t=271073