My Dell Latitude D820 laptop is locking up when I move it while open. The screen goes black and a green light comes on at the top of the keyboard that looks like a padlock with the letter A in it. None of the keys work and I've tried closing it and reopening it with no reaction. The only solution I have now that works is to manually power down and then repower. Is there some keystroke combination that will keep me from having to reboot? Any ideas about what might be causing the problem and how to fix it? Thanks for the help!