I called tech support awhile back and they said it was most likely a hardware error, even though I said it was all over the forum pages that this is a problem.  The technical support lady said that mine was two years old and probably ready for replacement.  I said to spend that much money every few years is ridiculous.  I was able to update the map by manually moving each file from the computer to the TomTom one at a time, tedious I know, but it does work.  You must be sure to copy the activation files as well, one at a time.  Good luck!  I now just tend to use my smartphone for any GPS needs.