In "power options" in Control Panel in XP Pro, I have set my computer to shut down the monitor after 5 minutes. This worked fine for 4 years. Two days ago, it stopped working. If I reset the option, and restart, it works fine ONCE, then stops working again (unless I reset and restart again).

Far as I know, I did nothing new to the computer recently to account for this. A Google search didn't turn up any answers I could use.

Thanks.

Don't know, any changes to antivirus or firewall settings?

Any new installed sw recently?