|What keyboard are you using?|
Some keyboards take up a heck of a lot of USB bandwidth. If you have a webcam plugged in & other USB gadgets, remove them.
That's assuming your new keyboard is USB and not PS/2.
Also, some keyboards come with their own software and drivers on a CD. Make sure you have the latest version. You can get the latest drivers by googling the make of your keyboard then going to the official website.
As you haven't said what keyboard you have I can't direct you to specific drivers etc.
PEBMAC - The biggest cause of Computing problems.
Usually caused when the user accidentally causes the ID10T Error.