Vista - Sleep Mode fails

I've read a little about Vista and Sleep Mode problems,
and nothing conclusive.
My problem is that when Sleep Mode is chosen, the computer
looks as though it is closing down, the screen goes black, I hear
my hard drive begin to shut down, then immediately restart,
bringing the computer back the the desktop view in the User
previously in use.

I read somewhere that perhaps an nVidia driver might be causing
it, and a jumble of other advice.

My devices are all up to date, including the ATK0110 ACPI UTIL
which MS kept advising me to load.

My power options are selected for maximum saving, having been on
the default.

Shut Down works properly.

Hi Perry,

Try looking through this sleep mode troubleshooting guide to see if it can help you. I would first check to see what is set to be allowed to wake up your computer in Step Four, then disable the "Wake Up" option for the one you believe is causing the problem in Step Five. The usual suspects are the network device and a wireless device.

http://www.vistax64.com/tutorials/63...-problems.html

Hope this helps you,
Shawn