'Build Project' has encountered a problem

I got an error message when I build the project:

Errors occurred during the build.
Errors running builder ‘CDT Builder’ on project ‘MyProjectName’.
Internal error building project MyProjectName configuration Debug
Merge conflict
Internal error building project MyProjectName configuration Debug
Merge conflict

Which tool are you using to build?
What is the project?
What would someone have to do to go from a blank, freshly installed Nano image, to reproduce this issue?