To elaborate a bit, for some reason the files associated with the Dark Forest were placed in the save folder prematurely. Starting the procedure for the initial entrance into a new area, at least part of the game got hung up on these files that were not suppose to be there yet, so some subsection of the transition was never mark as complete, and the 'save disabled' status not cleared.
Deleting the 5 *.x2 and *.2 files from the save folder and reloading it allowed the entrance to the Dark Forest to proceed normally.
