My PC won't go into sleep mode either automatically or manually so I just leave it on all day (the screen will go off at the pre-determined time though). However, that's not my issue as I've learned to live with it. I'm just mentioning it because it could be related to the following issue that just started happening yesterday.
When I come down to use the PC after it's been sitting unused for a few hours, the screen is off and I can still hear the fans running and the power light is on, as always. Usually all I have to do is hit a key or move the mouse and the screen comes back on and away I go. The last couple days though, the keyboard and mouse (both USB) appear to have "turned off" (no lights showing on either) during the idle period. Then, no matter what I do I can't get the screen to come back on because they keyboard and mouse have somehow went off.
At that point all I can do is a hard shutdown (holding the power button until the machine turns off) and reboot at which time everything's fine.
Anyone know what's going on? It's one of those "everything was fine for weeks and then all of a sudden" things.
This is a Windows 7 32bit machine, fully updated and no recent changes made.