Are you missing an assembly reference?

Question

I have created a class library project (Data Layer) that I would like to use is a Windows service project. I have created a solution that has both of these projects.  I have added the the data layer reference to the windows service reference and it shows up in list of references for the project.

When I try to build the project, the windows service project gives me the error that I am missing an assembly?

I have checked the bin and obj folders under the windows service project. the data layer.dll does not exist in either of them:
  obj\x86\Debug
  bin\Debug
I have tried manually moving the dll for the data layer project's bin to the folders that are missing the library.

Another interesting thing.  If I remove the reference and then add it again, the namespace will be available to me through the Visual Studio intelesense and the errors will go away.  Once I try to compile / build the solution, the errors return!!

Any help that anyone could give me would be very much appreciated.