audio "line-in" level

Powerbook G4, dual-booting 867.
In 9.2.2, the Sound control panel's audio-in level slider is greyed out.
All proper boxes are checked. (play-through, check level, etc.)
I can't adjust the level...it is fixed about halfway up.
It works fine on my Wallstreet. I even copied all relevant extensions and panels over to the G$ and rebooted....no dice.
What could be wrong?

Thanks all.

Trash sound preferences and reboot.

Copy the prefs over instead of the other items?

Make sure the right input source is selected.