Ipad mini disconnects from imac's USB ports
Since yesterday, my ipad mini keeps disconnecting from the imac after some 30 seconds of plugging in the lightning cable on any of the USB ports at the back of the imac. The battery charge goes on but the ipad disappers from itunes.
However, if I plug it in the keyboard or an USB hub, it does not disconnect. In this case the charge does not work.
Any idea on what to do?
Thanks.
IOS 6.1.3
ITUNES 11.0.2
OSX 10.7.5
iPad mini Wi-Fi, iOS 6.1.3