If you have AVG 8, I suggest you don't load the toolbar and you disable Active-Surf and Active-Search. OK. I'm not sure that Active-Search is a problem, but Active-Surf certainly is.
Every time you call a page on the web, this little monster checks with the AVG server to find out if it is safe to go there. It seems like a good idea, except AVG isn't coping with the load and you end up waiting for ages for the page you want to start loading.
However, it just got better. Clearly there has been something of a crash, ending up with every page call returning that the page cannot be found. I've disabled the protection and the pages are there just fine. The problem is AVG!