The issue it seems is arrising from TeamCity not following 'an element' of the project build order for a solution...
There are around 15 projects in the solution and most projects have dependencies which are observed by TeamCity...
However in this case one build order was not observed, so the dll was not compiled, and TeamCity said, "No, the computer says, No!", i.e. assembly reference failure.
Is there a logical reason for this as opposed to an aberation?
P.S. The solution builds without issue in Visual Studio 2010 (VS2010) from a freshly checked out SVN version, and upon inspection the build order for VS2010 is correct.
P.P.S. Is it because TeamCity looks for project dependencies and not build order?
For some background to this issue please look at