I'm running Ubuntu 12.04 x86_64 (though these issues have existed in previous releases too) and have a Radeon 6800 graphics card. I've run into issues with the open-source driver (the system would randomly hang when shutting down) so I switched to the proprietary driver (I compiled it myself using these instructions), but I am having new problems now.

The main issue is that when I go into sleep mode, about 50-75% of the time, the screen goes black but the monitor does not actually shut off, and I can hear that the fans/hard drive are not suspending either. I can't get the computer to wake up (Ctrl+Alt+F1,2,3,etc. does not work), and I always end up force shutting down with the power button.

I'd really appreciate help! Here is some information that might be helpful:

$ fglrxinfo
display: :0  screen: 0
OpenGL vendor string: Advanced Micro Devices, Inc.
OpenGL renderer string: AMD Radeon HD 6800 Series  
OpenGL version string: 4.2.11631 Compatibility Profile Context

$ dmesg | grep fglrx
[...]
[    6.718606] [fglrx] module loaded - fglrx 8.96.4 [Apr  5 2012] with 1 minors
[...]