I am having the same problem, both in IE 7 and FF. Only Opera doesn't have the issue. I was thinking that it's related to my aggressive blocking of ads via the hosts file. But I do not know for certain. Quite a pain in the head, since IE is my main browser.
There's another problem, even more annoying: hitting the back button does not bring me to the previous page. I have to hit it a number of times. Using the down arrow in the back button to check the page history brings up ads URLs. I have a picture of the problem
right here. Once again, this does not happen in Opera, even though the ads are blocked in Opera too, with the difference that they appear just as white bands, without the "..cannot display the page" message.