I have a new 27" sandy bridge iMac with 3.4Ghz core i7. It's running OS X 10.6.8. When I press the F11 and F12 keys on the keyboard to adjust the volume level, the volume control thing pops-up. I can even light up or turn off the little rectangles, but the volume level does not change. If I go all the way down, I'm able to mute the speakers. The only way I can control the volume is using the System Preferences->Sound->Output Volume slider. On my other mac computers this slider moves when I press the F11 and F12 keys, but not on this new mac. Does anyone have any ideas what might be wrong? It's starting to drive me nuts. Having to open System Preferences every time to change the volume is not convenient.