VSS logging "The semaphore timeout period has expired"

I'm protecting a server using DPM 2012. When the volume shadow copy is triggered it is failing with this error in the event log (Source = VSS, EventID = 12289). The error is causing all DPM protection to fail. I was wondering if anyone could point me in the right direction on how to find the root cause of the error. It only started recently...DPM has been protecting the server for several weeks before this. Volume Shadow Copy Service error: Unexpected error DeviceIoControl(\\?\Volume{31d537db-f811-11df-add9-806e6f6e6963} - 0000000000000144,0x0053c008,00000000004ACEB0,0,00000000004AE0E0,4096,[0]). hr = 0x80070079, The semaphore timeout period has expired. . Operation: Processing EndPrepareSnapshots Context: Execution Context: System Provider

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Rob