Yes, the slowness and partial loads are effecting everyone, but the "internal server error" on the proxy page only seemed to a problem for certain OSes.

Neil, is right, the proxy server is examining the user agent and throwing an error for Linux/X11 clients. So it isn't a TCP issue (that's what I was thinking wrt the kernel), but more simple.

I'm posting this now from my Linux machine after I installed the user agent switcher. I'm not mimicking Internet Explorer, but wrote my own custom agent, "Mozilla/5.0 (U; en-US) Firefox/3.6", to still provide a little information, but not leak so much about my computer to every website I visit.
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Pioneer VSX-1018AH-K, PDP-5020FD, DV-79AVi
Axiom M22s, VP150, QS8s
Sony PS3, surround backs
-Chris