Do you use any other antivirus in your computer?
RPC error is generally related to other antivirus present or, at least, firewall blocking.
RPC error may also be because of avast! services being stopped.
Anyway, RPC error is most likely correct by this procedure:
Go to Control Panel > Add/Remove programs > avast! antivirus > Remove. Then choose Repair function in the popup window (Repair). You must be connected to the internet while repairing.
If this does not help, can you uninstall / boot / install / boot again?