Yep, you're on the right track, kilgoretrout.
I tried everything I could think of, including newer/older kernels, newer/older nVidia drivers, manually running pm-suspend, etc. But it turns out the problem was damned Compositing.
With the new install, I decided to try and let X make all the decisions, rather than having an xorg.conf file. When I reinstated my xorg.conf then I now have Suspend and Hibernate working properly. This is what it looks like:
Code:
Section "Device"
Identifier "Video0"
Driver "nvidia"
VendorName "NVIDIA Corporation"
#**********************************
Option "NoLogo" "True"
Option "UseEvents" "True"
Option "AddARGBGLXVisuals" "True"
Option "DPMS" "True"
#**********************************
EndSection
# For MythTV VDPAU
Section "Extensions"
Option "Composite" "Disable"
EndSection
When that worked, I commented out my Device Options and tried again, and it still worked. So the problem is Compositing.
(BTW, AGP is way old and is not present on current cards)