I too have this problem! I have a rMBP that is only about a month old. It seems to only do this when I am using the Notebook part of MS Word. But now today after the message it locke up completely and required a restart - I lost everything new that had been added that hour. Any suggestions? The file is on
the local SSD drive. It has done this with almost every Workbook that has audio recorded. No other files have caused the problem.