Display resolution changes spontaneously

Vista Business, SP1
Dell Inspiron 640m with integrated "Mobile Intel 945GM Express Chipset
Family" display adapter

Every once in a while, the resolution on my display will change
spontaneously, when waking from stand by. I don't power off my notebook too
often, usually just switching it to stand by when moving it from my office
to home. Now and again, when I wake it, I'll find that the resolution has
changed by itself from 1440 X 900 to 1024 X 768.

Any idea why that might happen?

Thanks.

Ken Isaacson
SILENT COUNSEL, a legal thriller
www.KenIsaacson.com