At the end of the day, NVivo froze while shutting down. This meant that none of the day's changes were written to disk, because apparently it stores them up and writes them at the end of the session. We found a .tmp file in docs and settings -- can't remember the exact path, but it was named like the actual data file -- and this turned out to be a complete copy of the altered data, with the exception that the dates of recent changes had not been recorded. Backed up the original day-old file as "...last known good", then copied the tmp file over to the original filename, and everything should be good to go, but when M comes in next, she should have a good look to make sure nothing else has been lost.