The latest release of Ubuntu (Gutsy) which is in beta testing right now has a problem where laptops with ATI graphics cards will hard hang when you attempt to suspend. The screen goes blank but the suspend light (usually a moon or something) just flashes forever.
Here is bug with the insanely long bug comment thread:
Here is the workaround:
Create this file:
Put this in it:
This will allow you to continue to use the fglrx X.org driver but without the kernel module which causes the problem with suspend. . This means you get 2D acceleration but not 3D. So no cool Compiz eye candy. But at least you can put your laptop to sleep.