What changed (e.g. new software installed, configuration settings changed etc.) between when it worked and when problems arose? If it's running Windows XP then you could try rolling back to the last known good System Restore point (Start -> All Programs -> Accessories -> System Tools -> System Restore). Just to be safe and to rule out any nasties installed on your laptop you should review this thread.
its not one of the new aldi gericom one is it? My one does the same intermittently but not all the time.
I'll try to watch the behaviour to see if I can tie it down. No matter what the model and make tho, if its under warranty, Id definitely open a support call.
Is it XP? Did you recently install Service Pack2? SP2 can screw up some proprietary Power Management apps. Check and see if there are any updated downloads for your OS/HW.