I have a mac at home. I have two browsers on the MAC. Whenever I use Safari, and there are more than one Advertisements that pop up in the midst of the page, I don't get any items after the advertisement.
You may want to test the application on the all browsers, IE, IE7, Firefox and Safari. I think the ads are definitely causing an issue on Safari, because on Firefox, I am not able to reproduce the problem, in fact firefox doesn't even display the ads. (Which is fine by me) IE seem to work the best of all the three. Haven't tested it on IE7.
This seems to be happening with one particular advertisement. It's called timetotalk.org - it seems to be popping up along with another ad. So I am guessing it's because of the multiple ads in the middle of the page that's causing the problem.
-- SR