The job failed with the following error: The resource could not be backed up because an error occurred while connecting to the Agent for Windows. The correct version of the Agent for Windows must be running on the target computer.

I am gettting this error when trying to back up File shares (CIFS) from my EMC VNX san.

"The job failed with the following error: The resource could not be backed up because an error occurred while connecting to the Agent for Windows. The correct version of the Agent for Windows must be running on the target computer."

I'v gotten this error before and it goes away and my back ups start to run fine but I have never been able to figure out the cause.  I am backing these up as file shares and I have already enabled  " Selection of user shares" .  Its been about 3 months since I had this problem and I was never able to determine the solution it always fix's it self.  I can telent to port 12000 which I have set as the TCP dynamic port range.  I even tested ports 10000, 6101 and 6107 and all were open.  I rebooted the server and even the services.  Not sure why it would give me this error when there isn't even an agent loaded on the SAN.

Any idea what causes this or how to resolve/prevent it?