OT? Loss of display brightness control

[Chris Lim]

Hi, I upgraded my stock 450 Cube to 10.2.8 and now I intermittently lose
1. the brightness slider in the displays control panel
2. the slider is there but it doesn't control the brightness (slides but
brightness is the same)
3. slider refuses to move from brightest setting.

I'm using an Apple Studio Display 15"

Additional stuff? A firewire cable to ipod and a USB bluetooth adaptor.

Anyone had the same experience? I've looked at MacFixit and Macintouch, but
there doesn't seem to be any feedback in this area

Heelp!!!