I've been having a few problems with File based web projects (probably of my own making) so I switched to using HTTP (IIS) instead.  Unfortunately, this screwed my Team Build.

The solution is to manually edit the SLN file, as per the instructions here:  http://forums.microsoft.com/msdn/ShowPost.aspx?PostID=3968. 

This certainly fixed the immediate problem, now my tests are failing :{  Once I get these passing again I' should hopefully get a published build.  That will be a good achievement for a rainy Friday.