can't connect to server to update,also system restore won't work with avast runn

avast is 6.1.0.1367, xp pro sp3. Set for automatic update, but get notice cannot connect to server. I can do manual update. Even if updated manually, I get periodic notice that last update failed, try again. Have tried various solutions found on line, but no luck. I have other programs which do automatic update (Malwarebytes, Super antispyware) with no problem

avast is 6.1.0.1367, xp pro sp3. Set for automatic update,
install latest version....7.0.1426