I just got a brand new Macbook Pro (2.4 GHz Intel Core i5) with OS X 10.9 Mavericks preinstalled. It's working great and I love the retina screen, but I've had a recurring issue daily where the Keyboard and Trackpad suddenly become completely unresponsive.
It's hard to pinpoint exactly what I'm doing when it happens, but generally I'm in the midst of using Google Chrome and navigating around. It happens in the midst of use, not while I'm away from the computer. Some time after using the laptop for anywhere from 30 minutes to over an hour they just become unresponsive. I can't move the cursor at all with the trackpad. And none of the keys on the keyboard are functional at all. I can't change volume. I can't adjust screen brightness. No letters work. I can't use Command+Tab to switch between applications. The only thing that surprisingly works is hitting the Power button on the keyboard. This will shut off the screen. Then when I try to hit the Power key again it will prompt me to log back in with my password, but I still can't type or move the cursor.
The only thing that gets me back up and running is to hold the power button down until it completely shuts down. Then I have to boot everything back up and it works fine again for awhile until it happens all over again at some indeterminate time.
I'm not running any virtualization software so that's not an issue.
Best Answer
This is a known issue, and a fix is coming.
Sources: MacRumors.com, Apple Knowledge Base