Windows 7: S3 Screwup

This load is over three weeks old and I had not encountered any problems up to now.

Leave machine unattended.
Machine works its way into hibernate.
Still unattended will try to reboot.

When I return screen says windows failed to come out of hibernate. A choice at this point is to delete hib file and reboot into Win. Make selection and machine goes into loop. If I hit del and enter bios, do an F10 and ok, making no changes. It boots into Win. I've done a disk check and everything is reported as ok. The bios is set to permit S3. And win is set at its reccommended settings. I am still running but it's a real bummer when s--t don't play nice. I am looking forward to my preordered copy of Win 7. But need to understand this before then.

I Changed the power setting in the bios to "Auto" and the machine went into S3 and rebooted to Win this morning. I don't remember changing that setting prior to this. But I am the only one here to blame. So in my hamhanded state I must have tweaked it.