Turning on your firewall will not stop the RPC from crashing I dont think?
Go to start>settings> control panel> administrative tools> from there go into services.
Scroll down the list until you find RPC (Remote Procedure Call) right click on it and click properties.
Go to the recovery tab and choose to restart service on failure.
Issue temporarily fixed.
Next jump over to
www.symantec.com and run their free online av scan. or download AVG from
www.grisoft.com and use it. Its free and it works.
Thus your issue will be resolved.