Are you running ePO 4.6.9 or 5.1.2? If so, it could be the issue outlined in KB84951.
Thanks for providing KB84951. I read whole KB and finally i found that its not about versions its beacause of third party tool (Avecto) which we installed on our test client machine.
Thanks and Regrads,
I can't see kb 84951, Please give me this link website.