This happens with Fx3.6.10, ie9 beta (x86.x64), chrome 6.0.472.63 and silverlight is version 4.0.50917.0.
The only parts time the site appears to work is the 'about us' and 'email sign-up' tabs. All other options just make the page reload, except for 'Promotions' which sends the site into an infinite loop of reloads.
I am running W7 HP x64. Rolling back to Silverlight 3 makes no difference. Disabling browser add-ons does not help.
On a laptop running XP home SP3 the site works alright, but performance wise its very slow to respond. It works on IE8 and Fx3.6.10 on that laptop, with silverlight 4.0.50917.0.