P2V converting windows server 2008 Failure

I am trying Virtualize my windows 2008 Server , & unfortunately have been running to this error msg 1% after the converter starts. The Error Msg is "Unable to create a VSS Snapshot of the Source Volume 2147754767 (0x8004230f) can any one help? thanks

Thank you for all your posts.... The problem was the USB Devices.... as soon as I removed them it worked flawlessly... again.. as a side not I like to add that it will not harm if you put your VSS on manual if its on automatic.... that should do the trick!.....