The "Forums" link in the navigation (below the header) points to "/forum/" instead of "/forum/default.asp". While both paths should work the same by default (from what I understand), it appears that a server misconfiguration prevents "/forum/" from properly directing to default.asp. All I get is an error message.
For security reasons, I'd suggest the details of the error be hidden in the future. That said, I'm not a security guru, so whoever knows what they're doing should take care of things accordingly as necessary.
I'm surprised this issue has been up for several days without being mentioned. (Or perhaps it was already brought up in this forum.) For me, it's just an annoyance, but it's worth fixing.
Edit: It seems to be fixed.