This happened a few days ago too, while Windows Defender was updating this file was flagged and the update failed. This time it’s being flagged as Win32:Gremo.
See, http://forum.avast.com/index.php?topic=97291.0, same issue.
But it isn’t an FP, when WD update the virus signatures that it is installing aren’t encrypted or otherwise protected. So you have a resident antivirus installed, which is actively looking for such virus signatures and alerts when it finds them.