Comment 8 for bug 1096247

@Jeff: http://en.wikipedia.org/wiki/Magic_SysRq_key

it may be disabled, I can't recall if we turn it off by default or not, so do this:

# cat /proc/sys/kernel/sysrq

if it's a 0, you need to change it to a 1:

# sudo echo 1 > /proc/sys/kernel/sysrq

More info: http://askubuntu.com/questions/160426/setup-shortcut-keys-not-working