TF250020 error creating new Team Projects

Whilst working on our TFS2010 Beta 1 test server today I got the following error when I tried to create a new team project

TF250020: The following SharePoint Web application is not valid: http://vs2010.mydomain.com. Verify that you have the correct URL.

I thought this strange, as I was doing nothing I had not done before, creating a MSF Agile team project with default settings. What I did notice was that in the new project wizard I had the server URL as http://vs2010 but the error message said http://vs2010.mydomain.com. So I checked the alternate access mappings in the WSS central admin, only vs2010 was listed, so I added vs2010.mydomain.com as the Internet alias and it all leapt into life when I tried the wizard again.

Question remains how did this work before, operating system service packs maybe?