every few hours this desktop stops. it acts like it is hibernating but it is not. the monitor display is on, but the mouse and keyboard both go dead.
in order to get it working again, i am forced to reboot by powering off.
the event log shows messages like, "The previous system shutdown at 10:01:10 PM on ¿7/¿2/¿2012 was unexpected."
hibernate and sleep are turned off completely.
looking through other threads on experts-exchange, it appears that similar problems have been related to hardware faults, but in this case the timing is suspicious.. i got a trojan on the desktop, cleaned it off using McAfee, did some more clean up using CCLeaner. then the problem started.
a couple of other strange things that happened at the same time:
1) services that were set to Manual were starting up anyways.
2) when i would shut these services down, some of them would restart.
i disabled these services, rebooted twice, then re-enabled them and now they behave normally - they do not start up when they're set to Manual.
the desktop is a Dell optiplex 780 (Core2 Duo e8400) running Windows 7 64-bit SP1 with 6 gb ram and plenty of hard disk space.