Diagnosing cause of NVFBC_ERROR_PROTECTED_CONTENT

I’m investigating why a particular Windows 7 instance returns NVFBC_ERROR_PROTECTED_CONTENT when I call NvFBCToDx9VidGrabFrame(). If I enable the GRID\NVFBCLog registry key I see the NvFBCHWEncode.exe sample from Capture SDK 5.0.22 gets the same error.

Any ideas on how to identify what may cause the driver to claim there is protected content? This is a fresh login, with nothing like DVD or BluRay software running.

(P.S. It isn’t clear to me if GRID, the traditional home of NVFBC, is a better forum, or the regular Video forum is preferred now that NVFBC is spun off to Capture SDK. Hints welcome.)