Read this and examine your connection setup , maybe this will help.
I've had the older plastic Apple usb keyboard and Apple supplied usb extension. I've saved these items over the years. I also have the Apple aluminum keyboard with the Apple supplied extension cable. I've learned the hard way not to mix and match the extension cable with the Apple keyboard type.
When I bought my rMBPro with thunderbolt 2 ports it magnified the problem with my Apple thunderbolt Display.
What were the issues? black screen, no power to rMBPro, artifacts where half of the Display showed the Desktop, thunderbolt devices getting the "disk not ejected properly', OS X Mavericks or yosemite not completing its install, the usb mouse pointer jumping around needlessly.
What fixed my issue? After 8 hours of going from one thunderbolt port to the other one piece of hardware at a time I finally discovered that the OLDER model usb extension cable supplied by Apple with the older plastic numeric keyboard does not fit exactly right with the newer model usb extension supplied by Apple wit the Aluminum keyboard.
The common denominator was using the thunderbolt ports with the usb attached caused these problems because even though the design of the usb extension cable was similar it was different. Too loose but very difficult to observe. Once I used the Apple supplied usb extension cable to only the proper Aluminum Apple keyboard did the problems ALL go away.
It did not matter if I connected the mix and match usb extension cable to the Apple thunderbolt Display directly to eve not a usb hub or even to a Thunderbolt Dock. Problems developed that were not acceptable. Hope this experience of mine helps some of you posters.
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