Created attachment 46364 [details]
Several users have reported this problem in the Launchpad bug at https://bugs.launchpad.net/ubuntu/+source/linux/+bug/539851
This has been occurring at least since Ubuntu 10.04's 2.6.32-14.20-generic kernel, continued in Ubuntu 10.10 with various 2.6.35-based kernels, and is still occurring in Ubuntu 11.04 with Ubuntu's 2.6.38-7-generic kernel.
I have attached the original reporter's dmesg from their 02:00.0 VGA compatible controller : ATI Technologies Inc RV630 [Radeon HD 2600 Series] [1002:9589] - Subsystem: Info-Tek Corp. Device [18bc:3692]
I will follow up with another dmesg snippet from another user's HD4350.
Created attachment 46365 [details]
*** This bug has been marked as a duplicate of bug 31943 ***