I had this happen to my Garmin Legend last week while on vacation. I fixed my problem by doing a master reset. I found this info on garmin's website not in the manual.
1. With the poweroff, press and hold FIND, PAGE and CLICK STICK buttons and then press the POWER button.
2. Release all buttons and after 5-10 sec the welcome screen is displayed.
3. Place the unit outside in a clear view of the satellites.
4. After a few minutes the unit will accure the satellites and be ready for navagation.
5. You will lose any stored data, so you should save your waypoints and tracklog before you begin.
I hope this helps.