Hey everyone, I'm having a similar issue.
My Apple wired keyboard does not want to work anymore with my rMBP 13'' mid 2014. It all started after installing Yosemite a few months back. It was random and I solved it by connecting the keyboard to another USB port, but that does not work anymore. I have resetted the NVRAM and SMC, still doesn't work. The rMBP has 10.10.5 installed.
The keyboard works on any other computer (Windows or OSX). I'm using it right now to write this.
So apart from resetting the NVRAM, the SMC, and connecting the keyboard to another machine... is there any other thing I can try?