Comment 7 for bug 156113

I had the same problem (thinkpad R40, radeon mob. 7500, gutsy with all updates, radeon driver)
I am not using the fglrx driver which was implied as the culprit in some other very similar bug reports. I used the old Kernel from feisty for a while and that worked just fine for suspend, except that it broke a few other things (most notably atumounting usb-storage).

After reading this post I installed the hardy kernel and everything now works as expexted.