I have a Dell Inspiron 8600. The video hardware is reported to be ATI Technologies Inc Radeon R250 Lf [FireGL 9000] (rev 01); this is some kind of ATI Mobility Radeon. I'm running the plain 'ati' drivers that ship with Ubuntu, *not* the fglrx drivers.
Suspend appears to work fine (and it did work with this machine in the past, early on with Dapper and before), but resuming does not lead to the desktop.
Instead, the screen shows an effect that almost looks like a screensaver (but de-installing screensavers doesn't help, and it's not a screensaver I recognize anyway):
The screen start black but then slowly bleeds white from the edges of the screen, until the whole screen is more or less white (there is a bit of a greyscale pattern). There are also a number of colored vertical lines. The bleeding effect looks very screensaver like, though the vertical lines don't. After a while the screen is entirely white and the effect restarts.
The screen stays in this mode no matter what I do. There does seem to be some response to keyboard input: ctrl-alt-delete triggers a reboot after a while. ctrl-alt-backspace appears to have no effect, though.
I first encountered this problem midway during Dapper. It must've been introduced by an upgrade as early on in Dapper and before Suspend did work. Initially I thought this was my own fault - I installed the fglrx drivers, de-installed them again, and the suspend started flaking out about the same time. I started realizing something deeper was wrong than a hanging screensaver when de-installing all screensavers in the system failed to make the problem go away.
Nothing I tried seemed to make this problem go away, and recently I decided to do a clean reinstall of the OS with Edgy. No fglrx drivers have touched this installation. Exact same problem.
I fiddled some with the settings in /etc/default/acpi-support but this had no effect at all.
Thanks for your bug report. Could you please add the full output of 'lspci -vv' and 'lspci -vvn' to your bug report as an attachment? Thanks in advance.