Last week an entire section of a notebook was overwritten(?) such that all cells (headers, text, inputs, and outputs) were merely
Null. It was in a section of the notebook that I wasn't using at the time, but fortunately I noticed and was able to recover from a backup file without too much difficulty.
Today, I noticed a different, but entire subsection that exhibited the same behavior (I haven't yet recovered my work on this portion).
The only clue that something strange was happening was that last week MMA informed me that an outside program had altered the contents of the notebook, so it was saving a new copy. This happened several time last week when the issue first presented itself. I haven't seen it since then, however, so this symptom was apparently not present for the current case.
Here's what I'm running: OS X 10.9.2 MMA 22.214.171.124.
Hopefully this isn't a red herring, but the notebook does happen to be in Dropbox, which makes me wonder.
Has anybody seen anything like this? Any ideas?
Below is a screenshot of the original case.