adb backup disabled on phone
try a usb2 (instead of usb3) port: http://forum.xda-developers.com/showthread.php?t=2077799#6
do you have a sony? http://forum.xda-developers.com/showthread.php?t=1696320
check your command: http://forum.xda-developers.com/showthread.php?t=1851811#5