Mac Pro USB ports stop/start working intermittently El Capitan

I recently upgraded to El Capitan and suddenly my Mac Pro's USB ports would stop and start working sporadically.

I tried an SMC reset, but that didn't solve it... here's what did:

I have an older 30" Apple Cinema Display with the USB ports in the back of the monitor. I had my USB Apple keyboard connected to the monitor's USB ports.

I looked in Console and discovered that my usb devices were having issues. Below is my NexStar USB 3.0 dock:

10/5/15 2:45:53.000 PM kernel[0]: IOUSBMassStorageDriverNub::ResetDevice - hostDevice at locationID = 0x00800000 will be reset!

10/5/15 2:45:53.000 PM kernel[0]: USBMSC Identifier (non-unique): 29D140815A00273 0x174c 0x55aa 0x100, 3

WHAT SOLVED IT:

The short answer is, I stopped using the USB ports on the back of the 30" Cinema Display and now everything is peachy keen.