Yeah thats possible matt and was the path I was going down. The rear wiper is controlled by a module integrated into the column stalk controls, which I believe is on the same loom as the power for the CD player. It may be something has gone t*ts up and is short circuiting or causing interference.
Ryan, you'd have to check for a short circuit between the CD player wiring and rear wiper wiring; got a multimeter handy?
Either that or the relay for the rear wiper is causing interference in the junction unit; try switching it for another to see if that cures the problem. The relay number is T12.
Oh, and for future reference, whack this sort of thing in the "Stilo -> Technical" section
