I too, for the life of me can't figure out what's causing this.
If the axis is inverted (0/1), the clutch could be on/off all the time. But since he can drive off, that couldn't be a problem.
Just re-try the following:
http://upload.lfsmanual.net/im ... b/HowToAssignAxis_Ani.gif
Also, something that you could try (to see if you can pin-point the problem), is to use the gas pedal as throttle/brake combines and the brake pedal as the clutch. Reassign those axes and see if the clutch works as normal?
Or you can simply switch the pedals/axes (use the brake pedal for the clutch axis and the clutch pedal for the brake axis) and see if either work as usual...
Clutching loose straws here.