You might want to check out this posting on the Dell user forums:
http://forums.us.dell.com/supportfor...hlight=#M13901
I had been having trouble with my battery draining too fast and also my processor staying locked at 400Mhz, even when it's set on Auto.
Basically, if you turn OFF automatic beam receive, then do a soft reset, follwed by a power off then on, your processor will be locked at the highest speed. It won't scale itself like it's designed to do.
It's strange that a setting designed to SAVE battery power, can actually cause the opposite.