I have been syncing my iPhone to my Lightroom library for a couple of years. Recently, Lightroom will give me the option to import from the device, tell me the pictures already imported (normal,) and then, after 30-60 seconds of "Importing..." on the screen, it will pop up an error message saying "The following files were not imported because they could not be read:" (which is all of the files that are not already in the library.) This includes JPG's and MOV's from the camera roll. Once I click "OK" to dismiss the message, the iPhone no longer appears as an optional device in the Import window. I have to unplug the phone and restart Lightroom for it to show up again, at which time I have the same issue.
I've tried multiple cables, both OEM and not, and have no problems syncing with iTunes. Is there some kind of device preference that needs to be reset within Lightroom? I'm not sure if it's a hardware, software, or combination problem.