Kevin, Unfortunately, your question isn't a "dumb" or easy question. You said you've done several thousand acres without any problems. What has changed since you've started having problems? If nothing's changed, I would try the following:
1. Copy all the data off the Aero that you need to keep. If you're using it for scheduling or anything, synchronize with your desktop to get the data off the machine. 2. Do a hard reset on the machine. You can do this by holding down on the power button (on the front) while you use the stylus to hit the reset on the back. Or simply remove both batteries and reinsert. This will complete erase the unit and reset it as it was when you bought it. 3. Reinstall Field Rover II and try running it again.
I know of one other person with an Aero that was having some weird problems and the above fixed their situation. I'm not sure exactly what happened, but I suspect that something somehow got stuck in memory.