Notebook goes dark when I close lid, and stays dark when I reopen

This is the issue:
About 1 month ago I noticed that every time I would close the lid on my
notebook, then reopen it, the screen stays black. The power indicator lights
stays lit, and I can even access the computer remotely. I just can't use the
computer itself. I have checked the Power options control panel and it is set
to "when I close the lid do nothing". The only way I can get the screen back
on is to press the power button which puts it into standby (only one light on
the power indicators is on, and it blinks slowly), then I press the power
button again, and it comes back on as if there was never any problem. I tried
updating the chipset and video drivers but that did not help. I updated the
BIOS and tried a hotfix, but also no luck. I ran sfc/scannow, but also no
help. I ran the HDD Diagnostic tool, which did not find any problems. I did a
XP repair, but also no help. I ran memtest 86+.

I tried all of this with Dell Tech Support. I began looking at the Forums
and it seems that many people with all different types of notebooks have this
issue. It seems like it may be related to Windows but no one has found the
cure.

If you can help with this I would be most appreciative.
By the way, I also upgraded my system from XP Home to XP Pro. The problem
started in XP Home but continues even now.