Comment 2 for bug 281669

Bryce Harrington says in bug 280646:

"On the Thinkpad T61 specific issue, I discussed it with Peter Hutterer. It seems to be that on this hardware, the numlock key doesn't actually send events when the fn is pressed so we have no way of knowing that it is pressed. This was verified via gdb on the xserver. Scroll lock and numlock are shared, so fn has to be pressed to trigger numlock.

So it seems to be either a hardware or kernel bug."

This doesn't seem quite accurate: I do (at least sometimes) see key events for the Fn key. Also, shift+numlock also activates num lock, and shift definitely does show key events.