The real tragedy of this error message is that there is no way to show the excluded files. So you have to guess. In this instance, a random Thumbs.db file got into the Visual Studio Setup Solution (vdproj, and unfortunate extension that describes and unfortunate tools) and was subsequently excluded. When it came time to prune a directory of images, I was denied while deleting an IMAGES folder - with no way to figure out which file was hidden in that folder. Only a miracle and a hunch caused me to remove the stray Thumbs.db (it was certainly out of place). Then the directory was deleted without incident.
Time wasted: 13 minutes.
Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. I am a failed stand-up comic, a cornrower, and a book author.
Disclaimer: The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.