I don't run Vista, so I can't reproduce this problem myself, but if I understand the problem I might be able to make a fix for it (as I stated in the other topic).
Edit: here is the proposed fix. I've just found out that this exact fix was also described in the topic started at BU... so much for my credit
Download
Extract this file to your UnrealTournament\System folder, overwriting the existing file. Note: this fix is based on v451. Although it might also work on a v436 server, it's better to be safe than sorry. The v451 update can be obtained from
www.utpg.org.
It might be a good choice to make a backup of your original IpServer.u file first.