I’ve just started to have the same problem. It coincided with my loading DesktopX on my pc to do some cool skinning. Disable DesktopX at boot time Avast! loads OK. Enable DesktopX at boot time, Avast! won’t load its resident protection and gives this RPC error.

However, if I load DesktopX later (not during boot), everything is OK with Avast!!!

So, I finally installed the much-publicised “Startup Delayer” program to force DesktopX to load much later in the boot sequence. Problem solved! I’ve further configured it to give an orderly boot sequence of most of my autostarts so that they’re not all piling in at once.

http://www.r2.com.au/downloads/files/startdelay_v2.1b10.exe

It’s great!