This probably isn't related to Xorg. The problem occurs much earlier:
The key combo stops working after running
/scripts/init-top/console-setup from the initrd.
I will investigate further to find out exactly which of the actions of
said script causes this.
--
AltGr-ScrollLock does not work
ht
Public bug reported:
Pressing AltGr-ScrollLock should show the current register contents on
the console. (See "fn_show_ptregs()" in file "drivers/char/keyboard.c"
and http://tldp.org/HOWTO/Keyboard-and-Console-HOWTO-8.html#ss8.2 ) It
doesn't. Pressing these keys does nothing at all.
Shift-ScrollL