NUTTZ I've had the same problems a couple of times now.
Copy your jsmap.cfg file from the game "settings" folder and paste it into the TE "settings" folder. I don't get the forward and reverse buttons I want but at least I can "fly" the terrain.
It now occurs to me I might be able to manually edit the jsmap.cfg file and move those buttons to my throttle.
Edit: It works
0,-1,
0,-1,
0,-1,
0,-1,
1,12,But 1
2,17,But 2 <-- Backward
1,14,But 3
1,15,But 4
2,16,But 5 <-- Forward
1,17,But 6
1,16,But 7
Where {device},{buton} But #