rpc error

Avast has switched it self off when I try to switch on fatal error ver 8.0.1483.0 comes up also RPC error will not uninstall to reinstall at wits end
using Win xp 3 help please anyone thank you in advance

See if this applies to your situtation:
https://support3.avast.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=46&group=eng