Boo-
It could be a couple things. Something might not be wired right(although not likely if it used to work). You may have gotten a bum unit, I would call lowrnace/eagle and see what they say, that unit still should be coveered under warranty and they are really good about that stuff. The only ther thing i can think of is if you are using lake chips such a navionics or lakemaster with your gps feature, you need to make sure you have all the updates for the unit before running the chips, if you dont know if your unit is up to date, you can check it on the lowrance/eagle website.