The main.c belongs to a console project and the project is open.
The main.c is the only file in the project.
The projects' tab is hardly visible because there is no way to customize the tab's colors :-(
I can post the file or the cbp or anything that may help you. My screenshot shows the problem but is not very helpful when you try to fix a bug...
=EDIT=
Closing/opening the cbp does not fix it, too.