Found a solution for the Xgl problem where pressing Shift-Backspace caused the X server to kill itself!
Run the following from a terminal:
xmodmap -e "keycode 22 = BackSpace"
That should fix it. Thanks to the Quick and Dirty Hacks blog for pointing this out.
UPDATE: From what I can tell, looks like this is required to be entered everytime X is restarted (when you logout/login or restart the machine), so best to put the command in a startup script for your desktop so you don’t have to worry about entering it manually each time.