|Well, it sound like - as the error message says - one of the keys is stuck. Have you spilled any liquids on the keyboard recently?|
Anyway, inspect the keys carefully to see if any of them seem to be pressed further down than the others. You can sometimes clear this sort of problem by prising the key up, pressing it again, and so on until it frees up. Otherwise you may need to dismantle, or even replace, the keyboard.