Now i am not going to say this will fix the issue but it may be worth a try, first off make sure its the correct lead, one you have used before and that used to work for transfering data and charging the to the unit, and will also work other devices correctly when plugged into your pc/mac as it may be an issue with your usb port socket on the pc/mac. when you are sure that you have the correct lead and you can confirm it is ok and works. take the end that plugs into the nav and get yourself a small pair of pliers and very gently squeeze the conection and i do mean gently, until you get something resembeling the image below. i have done this and it did work, what happens is that the connections on the socket become worn and loose. doing this tightens the plug fit into the socket. as i have said dont crush it and be very gentle when you do it. it may or may not work for you its just worth a try and if DONE RIGHT will not harm anything. let us know the result. Do it a little at a time until the connection feels tight.