I'm having the same problem. I can get into the UGV but cannot drive it around or get any of the "crew" to respond to movement commands. On the plus side, the gun does work! :-)
Is the problem perhaps related to ACE in some way?
On another point, is there any way that a UGV can be "packed up" as it were and transported in another vehicle? I'm only asking because I think the SWORD would make a really good bomb disposal robot type scenario.