Same problem here. It's maddening. It happens once in a long while, maybe once per three weeks.
The keyboard and trackpad basically lock up and respond very slow. I can type a five letter word and get maybe one or two of the characters.
The ONLY way to keep typing the word is to slow down my typing and press one key at a time, very deliberately and slowly until that key shows up on the screen, then move to the next key.
After a few seconds, it goes back to normal. By the time I've got Activity Monitor up and running, it has gone back to normal. (Plus, if I had Activity Monitor open at the time, switching over would be difficult due to the input lag.) Checking right afterwards shows that CPU, Disk Activity, and System Memory were all within normal usage ranges--nothing was pegged at 100%.
I am running:
Mac OS X 10.8.3 (but problem happened with earlier versions of 10.8).
Macbook Air 2012
i7 2GHz
8GB RAM
(all stock, straight from the factory)
I do not run Chrome--it is not even installed.
I've brought it in to Apple and they replaced the keyboard and trackpad and reformatted my system drive, but that didn't fix it. In fact, the problem happened not too long afterward, even before I had installed most of my software back on the system.
It seems to happen the most in Apple Mail, although that may be because that's really the only software I do the most typing in.
I suspected that it might be the aggressive spell correction features in Lion and Apple Mail fighting each other, but I've turned off the auto correct as much as possible and the problem still occurs.
Anybody got any news on this issue? I can't bring the Macbook Air back in for service without being able to reproduce the problem consistently.