OPTIONS
This problem has to do with the top casing (keyboard). It occurs when the keyboard is replaced with another keyboard of a different model. Unusual power consumption of the new keyboard causes the random trip offs. For example if you try to use another component (eg inbuilt iSight Web cam) that shares the same USB hub, the keyboard/trackpad trips off. Also restarting the system trips off the keyboard/trackpad. There's a temporary fix though...
If the keyboard/trackpad trips off, use the system till battery dies and goes off by itself; leave it for about a day without charging, then plug in the charger and turn on the system. The keyboard and trackpad should come on.
When you have your keyboard/trackpad working; my advise is:
Never restart your system.
When you are through working with it, just close the lid (sleep), DONT SHUT DOWN OR RESTART!
Don't use the inbuilt iSight camera.
GOOD LUCK. Feedbacks would be appreciated