Apple USB Keyboard not working on 27" iMac (Intel Core i7) I have two similar iMacs (27" - i7 - os10.8.4 ) and use Apple's extended USB keyboards on both of them. After a power outage neither keyboard will work on one iMac (A) although both keyboards work fine on the other iMac (B). I have reset NVRAM and SMC on iMac A but to no avail. I have plugged printers into the USB ports and they seem to work fine. As it stands, the only way I can log in on iMac A is by using a Bluetooth keyboard, the USB port however remains "invisible"...

Thank you for your help.
Sorry this isn't really an answer but I can't post a photo in a comment.

I have a 27" iMac i7 as well, when I connect a Key Board/Mouse and an iPhone via USB in "System Information" I see this:



What do you see? 

Note that the two USB ports are on different busses.  Have you tried both of them?  You mentioned that bluetooth works; do the other USB functions work (Card Reader, iSight Cam)?