i've had a moto x, a moto x 2nd gen, and now the pure, and the first two had no trouble transferring pix to my IMac (i use "Android File Transfer"). but the Pure will NOT do it. i get an error message, telling me the unit is 'locked up', etc, but dunno what that means. no external hard drive (representing the Pure) icon pops up...and the Android File Transfer pop up window is empty. what to do? any help much appreciated. thanks.