The subject behavior will occur if you are running Windows XP SP2, or Windows XP SP1 with the 837206 hotfix, because the client computer does not pass Option 252 information to Internet Explorer.
To workaround this behavior:
1. Open a CMD.EXE window.
2. Disable the DHCP class ID ipconfig /setclassid "Local Area Connection"
Where "Local Area Connection" is the connection name.
3. Shutdown and restart Windows XP.