Same problem. Phone charges from the normal charger. But same cable connected to any USB port on any PC nothing happens. No charging, no driver enabled and no connection to Itunes. An Iphone 3 works fine with same cable. I have cleaned the docking port, and have tried to wriggle it and reinsert it repeatedly, but no reaction on PC.
Have looked at the manual for changing the docking port HW, but it seems rather difficult. Anyone had same problem and success changing the docking HW? Would be nice to know before I risk trying this!