Using FF v5 here with avast,no problems with speed of pages.But i dont have the internet security part just the free av,it may well be this that is slowing down the sites as it checks them before opening.
Just had a look at the features of Avast Internet Security - it appears it can/does scan in "real time" so as above see if possible disable that feature and then you should see a difference - if that is the cause.
ACOLYTE - I agree with your comments. I was making the suggestion to see if there would be any difference - I meant as a temporary measure although I forgot to say that - in view of the fact of the mentioned "4 days ago" by Buteman which seemed to coincide with the install of Avast. The problem he is having may have nothing to do with this - just a process of elimination. I was awaiting his reply.