Dimension 8300 /Vista sleep problem apparently resolved.

Dimension 8300, BIOS version A07 (10/1/2004, latest version).

Windows Vista Ultimate.

Monitor would go to sleep at proper set time intervals but would not "wake
up". This was with the Windows native driver for Radeon 9700 Pro installed
and with BIOS set to factory defaults - including power management.

Allowed the "newest" ATI Catalyst driver to download and install today
(12.2006, hah), no joy.

Went over to the ATI site and installed the very latest Catalyst driver.
Still no joy.

Went into BIOS under "power management", and DISabled "low power mode" from
the default enabled mode.

Seems like it's working, though I'm not sure exactly what else (if anything)
that might affect.

FWIW -

Stew

I was wrong. That didn't fix the problem, as it returned within 24 hours.

However, it appears that by defaulting the BIOS power management settings
(again) and then choosing a different "power plan" / "balanced" - and then
setting the monitor sleep settings manually while disabling the screensaver
has indeed worked.

I find the control panel/power options interface in Vista to be hugely
convoluted and unnecessarily so.

The system has now been running with these new settings for over 36 hours
and the monitor can now be successfully awakened with either the (Dell) USB
mouse or keyboard.

Oh joy.

FWIW.........