When resuming from suspend, my display never comes back out of power save mode with the Maverick 2.6.35 kernel. I first noticed this with 2.6.35-2, and today updated to 2.6.35-3 with the same results. I have installed today's daily mainline build from the kernel PPA, 2.6.35-999-061510, and this kernel does not have the issue. Standard Karmic and Lucid also work fine, so this is an Ubuntu specific regression.
When the system does resume, it appears to be functioning other than the display not being initialized correctly. The lock keys on the keyboard toggle the LEDs and I can hit ctrl-shift-alt-F1 to switch to a tty, and then ctrl-alt-del and the system reboots. I also tried booting in text only mode and manually doing echo mem > /sys/power/state, and still no video on resume. If I then blindly type vbetool post, the display comes on, but is all messed up since it is in the default VGA Text mode rather than the graphics mode that the console driver expects it to be in. This is all with the amd64 build using an ATI Radeon HD 4850. I can see nothing out of the ordinary when reviewing the syslog either; as far as the kernel is concerned, it thinks it resumed just fine.
Any pointers for further debugging are welcome.