I recently installed an Asus EAH5450 Silent 512MB GPU in my GA-MA770-UD3 mainboard. Two monitors are connected, partial xrandr output:

DVI-0 connected 1920x1200+0+0 (normal left inverted right x axis y axis)
HDMI-0 connected 1024x1280+1920+0 left (normal left inverted right x axis y axis)

Note that the 2nd monitor is rotated, and has a different resolution than the primary monitor. The system runs Kubuntu 11.04 Natty AMD64, pm-utils 1.4.1, custom 2.6.38.6 kernel with radeon kms. From KDE, clicking "Launcher: Sleep" suspends the system to RAM with no problems, but resume fails about 50% of the time. (Seems to work once, then fail the 2nd time.) When resume fails, the system and screens power up, but remain unresponsive. I can ping the system but not log in through ssh; the dreaded reset button becomes necessary.

With only the primary DVI monitor connected, the system resumes perfectly every time. But I want to run both monitors. Then I tried suspending by switching from KDE to a root console and running pm-suspend. Subsequent resumes worked every time.

Finally I copied /usr/lib/pm-utils/sleep.d/98video-quirk-db-handler to /etc/pm/sleep.d/98video-quirk-db-handler and commented out the --quirk-no-chvt line as follows

	elif using_kms; then
            # Using kernel modesetting?  No quirks, and do not change vts.
	    remove_parameters $possible_video_quirks
	    # FHM 2011-05-17: Want to use chvt anyway on my system
	    #add_parameters --quirk-no-chvt
	    echo "Kernel modesetting video driver detected, not using quirks. But DO chvt."

That did the trick -- suspend & resume from KDE have been working ever since.