So I'm stuck at the map screen early in Jagged Alliance 2. I got information about the helicopter pilot being somewhere around Drassen, figured that it's a sidequest that I could handle later, and sent my mercs south from the airport. Then I realized that they were in need of rest and healing, so I ordered them to retreat from the town, and now their location is displayed as XX. I have no idea where Sector XX is, how to get my troops out of there or what is causing the problem, and Mr. Chivaldori is telling me to get a bloody move on with the assignment already.

Can anyone help me out?

EDIT: I can click the destination column and try to choose a location, but all it does is say "This vehicle can only travel on roads". I have no idea what this vehicle might be or why my mercs couldn't just get the fuck out of it and walk if they don't feel like driving.