I would go with the above suggestion but if that has no effect
Load a Live Linux and see if the problem persists. If it does you have a hardware issue related to the New Keyboard and if it doesn't it's the drivers for the Internal Keyboard being shot under your OS.
You can get a Live Linux from here
http://www.livecdlist.com/
Or from your Local Newsagent as a Cover Disc on a Linux Mag. Just remember using a Live Linux has no effect on your existing OS unless you chose to install it. These run from a CD/DVD and contain most of what is required to load most hardware.
Col