MacBook keyboard error, only letters not working A couple of weeks ago I damaged the logicboard of my MacBook when I attempted to clean the keyboard. However, it worked perfectly fine if I had the lid closed and attached it to an external keyboard.
But it happened twice, that there was a triple klick sound from the MacBook internal speakers and my Bluetooth keyboard stopped working. I figured out that only a restart could fix the problem. 

Now, I got a new MacBook and transferred the system from the old one. Now it gets weird: the same strange clicking sound and the in-built keyboard stops responding. However only letters seem to be affected. Now I am wondering if it is a software issue that I carried over via the system transfer. Any ideas?
I had some similar issues with USB keyboards attached to an iMac. I solved this issue by deleting the contents of the Library/Caches folder from my user session (the Home icon) and rebooting the Mac.