I bought an iPhone USB cable thru eBay for a cheap price. It used to work fine but the last few days whenever I plug it in to my Early 2011 13" MacBook Pro it shuts off immediately. (other USB charging cables from apple etc. work fine with no problems) The strange thing is, it shuts off only in the USB port facing towards the trackpad but it works fine in the USB port towards the screen. I tested this on several 13" MacBook Pro's and got the same above results on all of them. Does anyone have any clue what the problem might be, and if the USB cable might be defective, and can this cheap eBay cables harm my computer? Thanks in advance for any help.