Hi,
What WIN dou you have ?
-a board search for the exact error message will help ..
-first make sure you are not infected by Blaster/lovsan and apply all necessary patches (see Board-Topics). Best RUN WINDOWSUPDATE until there are no critical patches to install.
-then try to restart the RPCss service and ensure it is set to automatic,
if the following reboot won't help, I'd advise a clean uninstall and reinstall of Avast