This problem is similar to others that I've seen posted but nothing was quite the same and the solutions that I've tried (e.g. rebooting or upgrading router) didn't help.
When connecting to the net from home, I can get to any web site that I want to just fine except those in the med.umich.edu domain (e.g. http://med.umich.edu). Using two other computers running XP at the same place, I can get in just fine. Also, when I am at work - and connecting within the internal network - it works fine. Also if I tunnel in via VPN, I can see them as well.
At home, I am accessing the web via a wireless card and ATT-DSL via a 2wire 2701HG-B Gateway and see the same problem whether I use FIrefox or IE so I think it is a system problem. Also, if I use a wired connection to my router rather than wireless it still doesn't work. Finally, when I connect from other sites at the University of Michigan outside of the Med School firewall, it doesn't work either.
Unfortunately, the UM Med School doesn't support Vista (I can see why with these problems) so it is hard to get help from them. I just tried upgrading to the Vista SP1-RC and that didn't fix the problem.
I suspect that this is something related to local vs internet security. I tried adding one of the sites to the "trusted sites" list but that didn't fix it. So, I'm out of ideas at this point.
Any suggestions would be welcome.