I don't know how I found out but I discovered that early MacBooks such as this one (which was the second edition) suffered from a "bulging battery problem" that Apple considers a safety issue. From a practical standpoint, when the battery bulges, it presses against the bottom of the trackpad and causes problems that can be a button that is difficult to press, an unresponsive trackpad, or as was my case, an over-sensitive trackpad. All you have to do is sight across the bottom of the laptop. If the battery is protruding, Apple may replace it for free (or, at least its worth asking them before trying something more expensive). Anyway, they replaced mine for free. Hope this helps should anyone have a similar problem in the future.