Somehow stuck in "sleep" mode...

I have been having a really wierd problem. I have double checked all my power management settings, and even put my computer in the "always on" option state. Sometimes, when I leave my computer on overnight, it will act like it is stuck in sleep mode with a blank monitor, and no hdd activity. I am really ****ed off, has anyone had the same/similar problem? I am thinking it might be a settingin the bios or windows.

Had a similar problem some time ago. Check the power management settings in your BIOS. You might want to disable *all* of them. I did.

A bit less common but has happened to me on a couple occations where the monitor itself as a built in power management setting.

But for the most part it's like FlailBoy said, check power management for Windows and the BIOS