Disabling all the calls to ClearState() avoids the crash (runs fine for 15 minutes).
[but I can't disable those calls in the "final" code, it helps me to be sure that "external" changes to the DeviceContext (shared by several middlewares) are reset to default]
I can't test on another PC to be sure it's ATI switchable specific [the office is closed for the whole week, and I only have this one with Windows 8]
If you want to give a try to this crash, I can send you an EXE by mail, just get in touch with me.
Have a good week-end