FWIW, the site works fine with Safari 5.0.6 under 10.5.8 (PPC iMac), and a bunch of (up-to-date) extensions active, including Ghostery.
More importantly and AFAICT, the site works fine too with Firefox 3.6.28. My copy uses a rather dated extension and plugin config, the list of which is quite long. You can get it quickly by selecting My Config > View My Config from the Tools menu. I agree with the suggestion that an extension is likely involved in the problem. The first step in troubleshooting that is to disable them all. Next, your extension/plugin config listing will allow us to suggest which one(s) is/are the most likely culprit(s).
