If, like me you use Nant to build many projects in one go, then after some time, the list of projects that need to be built can get quite large. All of the build scripts I run tend to build in release mode, though we build locally in debug mode.
I suggest looking through the build logs after adding a new project to make sure that it is actually being built. The other day, I added a new solution to the build and after looking in the logs found that most of the projects were being skipped. The solution was simple. Use the configuration section in the solution properties of Visual Studio to make sure that the mode that you are building in has the projects set to actually build the project. It sounds simple, but it could keep one guessing for a long time after a long week on a Friday afternoon!
Cheers
Rich