false warnings?

Everytime I fire up Foxfire, Avast is saying it blocking the browser from going to a website Something like:

Infection Details
URL: hxtp://20.ppcstream.com/feed.php?type
Process: C:\Program Files (x86)\Mozilla Firefox\f…
Infection: URL:Mal

I am ashamed to be using IE to post this …but this HP lap top seems to be the only
machine Win 7. My version on Win XP isn’t doing this,
Thanks, Craig
:-[