Please run:
xev | grep -A2 Button
and then middle-click in the little white window.
If it's working then you should see button 2 events, something like:
ButtonPress event, serial 37, synthetic NO, window 0x4800001, root 0x156, subw 0x0, time 1291392572, (41,108), root:(98,160), state 0x10, button 2, same_screen YES -- ButtonRelease event, serial 37, synthetic NO, window 0x4800001, root 0x156, subw 0x0, time 1291392692, (41,108), root:(98,160), state 0x210, button 2, same_screen YES
What do you see?
Please run:
xev | grep -A2 Button
and then middle-click in the little white window.
If it's working then you should see button 2 events, something like:
ButtonPress event, serial 37, synthetic NO, window 0x4800001,
root 0x156, subw 0x0, time 1291392572, (41,108), root:(98,160),
state 0x10, button 2, same_screen YES
--
ButtonRelease event, serial 37, synthetic NO, window 0x4800001,
root 0x156, subw 0x0, time 1291392692, (41,108), root:(98,160),
state 0x210, button 2, same_screen YES
What do you see?