I think I figured this out. If you a using a report, or a view within a report, where the vertical column has conditional formatting or some sort of calculation/formula embedded, it will not allow in-line text editing. I think***** this is the reason why.
As soon as I removed conditional formatting from my view, it allowed me to start editing my column with in-line text editing. I had a field called "Resource" where I would type-in the name of the main graphic designer we predicted would work on the project (before the project started). I had conditional formatting set up so anything that was blank would automatically display the text "TBD". This conditional formatting setting prevented me from doing in-line text editing.