I had the issue with Firefox 5.0/6.0 on Windows Vista Business recently. Many pages with double click ads did not load completely. They just sit there partially loaded until I pressed F5 or CTRL+R to refresh the pages. I couldn't figure out the reason that it ceased working. It was working. Also I tested the same page http://bettereducation.com.au/Results/vce.aspx on other machines with Windows 7 and found no problem.

I used Firefox "Tools\Web developer\error console" and found it's caused by "Security Error: Content at http://googleads.g.doubleclick.net/ may not load data". Then I tried turning off AVG Surf-Shield from AVG Toolbar Options > Security. It fixed the problem.

There are other ways may help solve the problem. For example,


Visit http://www.google.com/support/forum/p/AdSense/thread?tid=4035c2c129d34680&hl=en for details.