I spilled coffee over my mac's air keyboard yesterday. The computer seems to work but the keyboard doesn't. The symptoms:

* The laptop boots into the drive selection screen every time (alt key constantly pressed?)
* The caps lock, arrow, enter, esc keys all seem to work
* I can't enter my password at the boot screen. Some key-presses seem to be registered but obviously not the correct ones. For example, pressing the N key once doesn't show a keystroke, but pressing it twice does. It feels like there's some function/alt/ctrl/shift key that might be constantly pressed, but I can't tell which one, or make it behave differently by pressing those.
* An external keyboard (either bluetooth or usb) doesn't behave differently
* If I choose the guest mode, the computer will boot into the Safari only mode. The same thing will happen there - some keys will show wrong signs when typed in the address bar, and at some points the keyboard stops responding.
* The external keyboard however seems to work in that guest mode.

Questions:

* Can you help me understand what exactly is the problem with the keyboard?
* Can anyone think of a way to log in to the regular mode?
* Assuming the keyboard is the only thing broken, can it normally be serviced on a Macbook Air?

Thanks!