I found a strange behaviour in a Revit MEP* Space Schedule today. When I miss-clicked in the column "Occupiable", didn't hit the tick-box, subsequent edits showed a "grey out" state and the change was not applied. I can't find any reference to this in the documentation, which doesn't mean it isn't there, so wonder if anyone out there knows what it means?
E.G. (see the animation below in the extended post): Click on a ticked item & it shows a grey tick, and stays as "Yes" in the schedule, rather than clearing to become No.
* Tried this in 2009 WU2 & WU3