Recover Keyboard mapping (alt+tab not working anymore)

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http://askubuntu.com – As I wanted to try Ratpoison and other mouseless window manager, I used this .xinitrc There's a keyboard remapping in there and i'm afraid (but not sure it's this...) it messed up my keyboard settings. Since, I've deleted this file, however, my alt-tab shortcut hasnt been working anymore. In the keyboard shortcuts section, the "switch application" shortcut IS assigned to alt+tab. More over, if I try to reassign this shortcut, and then press alt+tab, the alt+tab shortcut appears and is saved as expected. However, the shortcut doesnt produce the wanted behavior. Any idea why this happend an (HowTos)