USB keyboard not operating

I use the wired 10-key keyboard, and I disconnected it to clean it. just wiped the keys gently with a multi-purpose cleaner and now it's dead. No response at all. (using the wireless keypad right now). I've check all the USB ports and all of them are functioning (IMac is just one year old). I also did a cold re-start and even unplugged the power cord for 30 seconds.

Apple says there is nothing to do, and I find this really odd. Anyone else ever have a similar problem?