sometimes when my system starts i don’t have avast resident scanner running and when i try to activate it ,there’s a message saying that there is an RPC error of some sort.
help me out guys! :o
FAQ is very helpful sometimes 
Can you try to repair your installation?
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?
Do you have any other antivirus installed in your computer?
Did you have in the past? Which one?
Do you use a firewall? Which one?
Also, take a look into Administrative Tools > Services
and see how the four avast services are set to start (automatically or manual).