Have you changed your power settings at all or maybe a program has changed them for you.
Open control panel, performance and matinence, power options
There should be a box on there that says turn off moniter and you can set the time.
Hope this helps
For some reason, sometimes my monitor won't shut off after 5 minutes like it's supposed to. I have tried the process of elimination, but I stil can't figure out what it is. The main problem is sometimes it does it, and sometimes it doesnt. Is there any type of prog I can use to tell me what is interrupting the process? thanks