Weird error for build specification

[LarsM]

I deleted some files from my project, and suddenly my build specifications aren't working anymore:

If I choose properties for "visualize", i get the error message:

Choosing "build all" from "Build Specifications" seemingly still works. I've tried deleting all project files and making a new project, but something is still amiss. Any clues?

[LarsM · Accepted solution]

OK, I threw out all files, made a new directory, rebuilt, and now it works. Dunno what went wrong though.