The T2S_MentalRay addon includes copies of Softimage DLLs, such as sibase.dll, and that causes problems in Softimage 2011. I’ve had two cases of shader/workgroup problems that were resolved by removing this addon.
Update: As noted in the comments, the problem is older versions of SPDL files that contain GUIDs used by the Softimage factory shaders. Addon shaders are loaded first, so these SPDLs override the factory defaults and cause problems.
A Subscription customer reported getting this error during the Softimage 2010 SP1 install. I also saw this reported on the AREA for ModTool. However, these are the only two reports of this error that I have ever seen.
Error Number: 0x80040707
Description: DLL function call crashed: gdi32.DescribePixelFormat
Setup will now terminate.
The customer worked around the error by installing in Safe mode, but later had problems loading his C# plugins. So we tried a silent install of Softimage 2010 SP1, and that seemed to do the trick.