A couple of years ago, my 660LM started acting up. I did a complete reset of the unit and updated the software and maps, and it's been working fine ever since. I'd have to look for the instructions for doing the reset, but it involves holding down the button and one corner of the screen. (As far as I can remember) When I plugged it in the computer, a couple of weeks ago, it did another software update as well as map update. Before I did the complete reset, mine even had the time of day wrong by a half hour!
Found the instructions on YouTube.
If you have routes or favorites saved on the GPS, save them to a computer before doing the reset.
John