I cannot edit or add a path to a referece file. I have inherited a project at work. Whern I open the project and go to the references scetion in the Visual Studio 2012 IDE there are some little yellow warning signs showing that there is something amiss with the reference listed there.
But when I click on the item and look at the missing path, I find that the name "Path" is in grey suggesting that I cannot edit it and, sure enough, I cannot add the path name to the adjoining field. What causes this? I have the solumtion file and the project file checked out in edit mode.

The project file had a hand-coded reference that was wrong.