VS2008 / TFS Build 3.5 / Ent Lib 4.1

I have a rather large solution that contains several apps. They are all currently using Enterprise Library (v.4.1) for their data access layer. 

I added and locally tested a new data access layer that uses LINQ to SQL- it was fast and easy to add and the test went fine. But...

When I checked in the project, it would not complete the build - I get a "Partially Succeeded". There are some warnings, but those exact same warnings were there prior to the build failing.

I took the data access class back out (along with the code that calls it) and rebuilt and it builds fine.

I then added an empty new class and put a single variable in it and referenced it from the code. That built. I then created a new LINQ to SQL class in that new project and did not even reference it. When I checked that in, the build failed again with the "Partially Succeeded" message. No extra errors or warnings.

I love LINQ to SQL, I have used it in a few projects outside of this system, but I now have many hours into attempting to get this to build with no success.