Hi Sébastien,
thanks -- let's hope we can narrow down the issue. The problem seems to be that Org is confused when adding the overlay for displaying the new date in the agenda. This generally happens with headings that have special text properties or overlays already, like links. Try to remember the actual content of the heading next time you stumble upon this bug, it may help finding the problem (e.g. does the heading ends with a link?) Thanks! -- Bastien
