This started happening sometime tonight. Clicking on a thread puts 5 entries for ad.doubleclick.net into the browser history before loading the thread, making it tedious and annoying to navigate through the site using the back button.

 

I've tried to replicate this but not currently seeing it despite various forums and threads I've browsed around in via IE (normally I use FireFox - but I used IE to try and replicate this issue since you are using IE 7?):