This is a problem caused by the change between Beta 1 and Beta 2.
To fix, check the following 3 regkeys -
Under (expand) InProcServer32, look for the presence of a non-220.127.116.11 (example 18.104.22.168) and remove it.
It has a reference that causes this to break.
If you do not have this MMC interface, you can use aspnet_regiis.exe aspnet_regiis -s
where path equals the location in the metabase where you want the mappings to change.
Note: There is also a switch to do this non-recurvisely if you desire.
and Stebner's VS.NET 2005 beta removal tool: