Lately I have been having a very strange issue with my keyboard. Randomly it becomes unresponsive, but not every key?! All letters are unresponsive, however I am still able to navigate spaces using cmd-1,2,3,4 etc and the caps lock button will turn on, however I can't type anything. The only way to resolve it is by putting the macbook to sleep and then waking it, any idea why this is happening, and how i can resolve it?