Problem: The Virtual Server admin page (:1024/VirtualServer/VSWebApp.exe">http://<hostname>:1024/VirtualServer/VSWebApp.exe?) on a multi-homed host system isn't accessible if one network card goes down. You get lovely HTTP Error 400 pages.
Solution: Check that the IIS Virtual Server site isn't bound to one specific network adapter. IIS manager -> Web Sites -> Virtual Server -> Properties ->IP Address. You can bind the site to one specific IP address, or simply select "(All Unassigned)" in which case you're not dependent on one NIC.