I can concur with Tye in saying that the problem is most likely because you are using NS and access to the site where the banner ads are stored experiences problems (bandwidth or otherwise) from time to time. You can confirm this easily by clicking the stop button after loading a page before allowing it to time out (be sure to wait at least 8-10 seconds). My guess is that the entire page will show up except for the banner ad. Granted, unusual things happen occasionally at PM but those are rare in my experience.

I have found that IE 6+ does not behave the same way (due to a caching strategy perhaps), but then I don't like IE and have decided to live with the occasional glitches. Either that or begrudgingly use IE temporarily.

--Jim