Goes into sleep mode even though I have "Put computer to sleep"=ne

I know there have been a lot of posts about people having problems comming
out of sleep mode. But I having a problem with mine going into sleep
mode(and of course comming back out). In power settings I have "put computer
to sleep" = never, but if I leave it sit over night it apears to go into
sleep mode and I can't recover it. I end up having to shutdown and reboot.

It MAY be a leap to assume it's going into sleep mode, or any other mode,
but what I'm seeing is that the fans are on, power light is one, but I move
the mouse, hit spacebar or anythign on the keyboard and nothing happens.

Maybe I'm way off base on my assumptions, but can anybod provide some
troublshooting ideas?

This is a clean install on a new system
64 X2 4600
2gb ram
6600gt 256 video
EIDE hard drive