Since Yosemite is now Generally Available, I decided to download it and install it on my Late 2013 Mac Book Pro Retina, 15 inch edition.
That was a mistake.
My USB Keyboard no longer works; and given the internet results, it seems that’s a common problem.
I guess I need to treat Mac OSX releases like I do Windows releases: Always wait for SP1.
I’ll update this post as I know more.
Edit: I’ve tried the steps in this content farm article to reset the System Management Controller, No Dice.
Edit 2: After resetting the SMC and walking away from my computer for 20 minutes (enough time for it to be asleep for 10), I woke it out of sleep and it recognized the keyboard again.
It’s unclear whether resetting the SMC is a requirement; but it does work now.
For reference, I have a Microsoft Natural Keyboard.
I had exactly the same issue – Apple USB keyboard with numeric pad no longer works (caps lock does not light either) with my late 2013 iMac.
I found a solution that may work for others: I plugged my keyboard into a Windows PC (Win 7, but probably not relevant) to see if it was dead and it was detected, but failed to install correctly, not surprisingly. This confirmed the keyboard still worked as caps lock would light. To my surprise when I plugged it back into the Mac it worked fine! No idea why, but it may be worth trying.
took me forever to get mine working. What I think did it was a combo of an SMC reset and plugging the keyboard into another computer that recognized it. Basically: put the keyboard in another computer and made sure I could use it. Then shutdown and unplug my imac (power cable disconnected from wall and imac). Waited 15 seconds. Plugged the keyboard in. Put the powercord back in, and started up. It finally saw the USB keyboard and could login. When I did not do the SMC reset or I did not plug the keyboard into another computer first it did not work. Others have found some success doing similar things. Hope that helps.