sleep scheduled by power management fails

Problem: sleep scheduled by power management fails, but sleep button works.
History: system built March 07 and can sleep but can't resume.
Nvidea driver update addresses this issue, sleep is hunky-dory
for a while.
Random infrequent Nvidea driver crashes require a couple more
updates and hot fixes. Crashes go away, but now "sleep after 30 minutes"
won't work. Sleep button works, but when resuming for a scheduled unattended
task PC won't go back to sleep without intervention.
(Coincidently with the scheduled sleep problem, the audigy
sound fails and requires an occasional restart to get back to work.)

Is this a known Nvidea issue? (I've reported to them--no response)
Any ideas?
Thanks to all!
B.