I had a similar problem (though mine where game-port pro-pedals). the problem came down to the wires being broken right where they come out of the pedals. likely from being kicked around under the desk, and having the cable pulled tight.
I pulled the cover off of them and checked continuity from the internal connections to the pins and found a few that where bad.
all I had to do was cut a few inches off the cable and re-soldier it.
then I put a loop in the wire where it left the pedals and taped it to the base, so when the cable is pulled tight the stress is spread over a wider area instead of on the hard plastic case.
so far the repair has held up for 4 years with no more trouble.
while I was in there I cleaned them up inside and lubed the slide-tracks, even 4 years later they are still smoother than when new.
it's fairly easy to check for without opening the pedals up. all you have to do is open the 'game controllers' window and then hold the cable to different positions where it enters the pedals. if it switches from 'OK' to 'not connected' as you move the wires, then you know thats the problem
