(Updated to correct an error: You want to enable DCOM for Authenticated Users rather than Everyone.)
On Windows XP SP2, you may no longer be able to open the Administration Website, although you could before you installed Windows XP SP2. This is due to tighter security measures in Windows XP SP2. To fix the problem, either uninstall and reinstall Virtual Server, or else do the following:
If you've installed (the currently pre-release version of) Windows Server 2003 SP1, the same issue may exist. If you can’t open the Administration Website locally, you can try configuring your LAN settings so that the proxy server is bypassed for the Administration Website URL, as follows.
You can also try changing the DCOM configuration, as for Windows XP SP2. The UI is slightly different, though: