how can i fix my ford galaxy's electric window?

one of my rear electric windows wont always wind up or down,i've tried swapping the switch with one from the front but it still wont work,even the switch for that particular window on the drivers door wont operate it,ive even tried using the central locking to close it.I took the car over speed bumps in the hope of jogging a loose wire,after trying everything again,i drove up the road,tried the switch & it wound back up.If anyone can tell me what the problem could be & how to fix it i would really appreciate it.Thanks!

PETE
September 2008