version 6.0.1125 internet access problem

I’m using the free Avast on one of my home computers, XP sp3, with four users. Three of them are restricted. when a restricted user loggs off while an administrator user is logged in (fast user switching) Xp hangs befoe rit gets to the login screen and only hard boot helps. switching off Avast shields before logging off from the restricted user account enables switching. this was the status before moving to version 6.0.1125.
I have not tested user switching since much more annoying phenomenon happens - NO internet access. home networking - yes, internet - no. switch web shield off and internet returns.
Time to part company?!

the above-mentioned upgrade was done using the GUI. Experiencing the described problems, I uninstalled the existing avast and reinstalled the 6.0.1125 distribution downloaded from the site. this fixed the internet blockage. It is yet to be seen if this also solves the fast user switching problem (need some time for other users to login and do whatever they do before logging off - a quick, ad-hoc test may not reproduce the conditions).
not parting company yet…

Which was your antivirus before avast? How did you uninstall it?
Firewall?