External Keyboard Fn+F3 won't dim the screen on Z61p/XP.

[AMATX]

I recently started using a couple of USB external keyboards(Lenovo # 55Y9003) on a Z61p/WinXP and a W700/Win7. Both work great...except on the Z61p/XP, where I can't dim the display anymore via my usual Fn+F3 key combo. However, if I press Fn+F3 on the laptop keyboard it works fine. So, I don't think my settings are wrong, it just won't work from the external keyboard. Btw, Fn+F3 works fine on the W700/Win7 laptop's external keyboard.

Other Fn+Fx key combos work as expected, it's just this particular one, which happens to be the one I use most

Any ideas/suggestions??

[RealBlackStuff]

Swap the external keyboards, to see if the other works on the Z61p.

[AMATX]

Good idea; shoulda thought of that myself...

Nogo, tho. Whichever one's plugged into the W700 works fine; whichever one is on the Z61p doesn't work. Even tried different USB ports; same result. Frustrating thing is that the only key combo that doesn't work is Fn+F3.