The RPC is an essential windows services and if it weren't working then very little else would work.
Yes AV is anti-virus and what is probable more important is was there ever another AV not just there isn't now, as this is a classic error with the presence of or remnants of another AV.
If it is a no to no other AV now or in the past, then try this.
Try a repair of avast. Add Remove programs, select 'avast! Anti-Virus,' click the Change/Remove button and scroll down to Repair, click next and follow.
If that doesn't work try, uninstall, reboot, install, reboot.