I have a solution which uses Solution Folders to split out the projects. In the Visual Studio IDE, the solution builds fine.
However when running the build using MSB
It is possible you may also have an issue where the line could have gotten in here with a merge conflict where it wasn't deleted when a project was deleted. If you can't find any other references in your project with a global search of the GUID, try deleting the line in the .sln
file and rebuilding.