If it was not on my system as you maintain how do you explain.

Every click on the KAT website caused Avast to produce the HTML:Iframe-inf infection warning.

After I had cleared caches, temp files, run Malwarebytes, etc. Avast still produced the HTML:Iframe-inf infection warnings only on the KAT site.

Now without touching or doing anything else I uninstalled then reinstalled Avast and the Warnings ceased completely and these warnings have not reappeared since.

The Avast reinstall was exactly the same program and virus definition version as previously.

So if this problem was not on my computer how do you explain that simply reinstalling Avast without touching anything else caused Avast to cease issuing HTML:Iframe-inf infection warnings?

It would appear that Avast had somehow been infiltrated or contaminated in some way that was causing Avast to raise false positives and the reinstall somehow cured this problem.

As I say I can go to the KAT site now and do everything that I did before that would have raised Avast warnings but now I can go there and I have not experienced one warning since reinstalling Avast.

P.S. I am using Firefox 8.0 beta I was using 7.0 but upgraded to 8.0 because I have a lot of trouble connecting to the Avast site but this connection problem still remains.

Firefox sits there for ages with the black arrow spinning anticlockwise before it finally goes green and connects.

Hope this information provides enough help to lead to an answer.

Thunder Bird.