Given that this problem can occur with older ATI graphics cards (such as the Radeon HD4350 in the report I mentioned in comment #24), users of older versions of Ubuntu will be pleased to hear that the abovementioned patch is included upstream in kernel 2.6.33.15 (Ubuntu 10.04 "Lucid Lynx" uses a 2.6.32 based kernel but with DRM from the 2.6.33 kernel series).
Given that this problem can occur with older ATI graphics cards (such as the Radeon HD4350 in the report I mentioned in comment #24), users of older versions of Ubuntu will be pleased to hear that the abovementioned patch is included upstream in kernel 2.6.33.15 (Ubuntu 10.04 "Lucid Lynx" uses a 2.6.32 based kernel but with DRM from the 2.6.33 kernel series).