I had to do some work in a VS2003 web service today. I have a remote web server and when I went to debug the service, I got the error message "the RPC server is unavailable." I suspected a firewall issue, though I did not know if I needed to attack the firewall on the client side or the server side. Luckily, my first attempt did the trick. I was reminded (thanks KBAlertz) of this MSDN document that I remember going through when moving to XP SP2 last year. I looked at my firewall and saw that the ports which I opened up via this document were not listed. So I just redid them and voila, all is well again.