I bet that's the accuracy circle.
Go to the main menu/setup. Then go to the 'map' tab on the left. At the top of that page, move over to the "other tab" , and on that you should see on top the 'accuracy circle'. Turn it off.
Edit: If you lost your owners manual, you can download or look at it here:
http://www8.garmin.com/manuals/GPSMA...nersManual.pdf
I used to have that unit and loved it.