I have a Thinkpad T42 with Radeon Mobility M6. S3 sleep works fine, usually.
Today I've started compiz instead of metacity. It works reasonably well. However, if I suspend my laptop with compiz, it becomes unusable after resuming. The screen shows a text console (radeonfb) with some kernel messages (something about overcharge on USB ports; I usually see those every time on suspend/resume). The keyboard is nearly dead: CapsLock does nothing, Ctrl+Alt+F1 does nothing, Ctrl+Alt+Backspace does nothing. Alt+SysRq works, although no kernel messages are shown on screen.
I can ssh into my laptop at this state. dmesg shows no error messages or oopses of any kind. I can see all my desktop processes running (gdm, X, compiz.real, firefox, NetworkManager, etc). sudo chvt 1 hangs until I press ^C. sudo /etc/init.d/gdm restart takes a long time stopping gdm, claims success for both stopping and starting, but nothing changes on screen and I still see all my desktop processes running, not killed. I can attach strace to X, but it shows no activity. I cannot attach gdb to the X process -- I get "permission denied" even though I run gdb as root.
sudo reboot reboots the computer in an orderly way. I can see the usplash progress bar while the machine is shutting down -- that's the first thing that's updated on screen.
It is not just Compiz. Yesterday I started the Metacity compositor briefly, then turned it off. Last night I suspended my laptop and this morning I got a blank screen and a dead keyboard (no CapsLock) on resume.
I could ssh in. The last line in /var/log/Xorg.0.log was about resuming AIGLX clients after a VT switch.
I could kill gdm and X, but nothing significant happened. When I tried to start a new X server it complained about /tmp/.X0-lock. I removed that file and tried again. X printed its about message and then froze. I pressed Ctrl-C, then X unfroze, printed
(**) RADEON(0): RADEONPreInit
and a bunch of other messages, briefly showed the standard X stipples and shut down. Among those messages was something about being unable to initialize DRI.
When X shut down, I got a screen full of black and white garbage.
chvt 1 doesn't work.
sudo reboot appears to be the only way out.