are you going to www.jointedrail.com or a subdomain (or a typo). going to your profile page on their directly without logging in could display that error.
You usually don't get a 403 error for this, but I'd check to make sure you're internet isn't passing thru a filter somewhere. Usually they return with their own errors but a 403 could be a cheap way for the filter to block it. Alternatively try another browser (like Chrome.)
I have Windows Vista on a computer here and Chrome works fine. And the JointedRail site looks normal. Really sounds like something else is going on. What are you using for Virus, Firewall, Spam protection?