I was also getting this error, but I noticed that running !DumpStack does give me a trace when !ClrStack does not.
According to this link it could just be a thread that has been scheduled but is not running. In other words not necessarily a problem. I'm not sure why the clrstack command doesn't work though, possibly an sos bug?
0:037> !clrstack
OS Thread Id: 0x57cc (37)
Child SP IP Call Site
GetFrameContext failed: 1
0:037> !dumpstack
OS Thread Id: 0x57cc (37)
Child-SP RetAddr Call Site
000000000772f688 000007fefdb210dc ntdll!NtWaitForSingleObject+0xa
000000000772f690 000007fef5ca36ca KERNELBASE!WaitForSingleObjectEx+0x79
000000000772f730 000007fef5ca3a97 clr!CLRSemaphore::Wait+0xaa
000000000772f7f0 000007fef5ca3c20 clr!ThreadpoolMgr::UnfairSemaphore::Wait+0x140
000000000772f830 000007fef5cb21ff clr!ThreadpoolMgr::NewWorkerThreadStart+0x2a7
000000000772f8d0 000007fef5cb0582 clr!ThreadpoolMgr::WorkerThreadStart+0x3b
000000000772f970 00000000778d652d clr!Thread::intermediateThreadProc+0x7d
000000000772fb30 0000000077b0c521 kernel32!BaseThreadInitThunk+0xd
000000000772fb60 0000000000000000 ntdll!RtlUserThreadStart+0x1d