ISight not behaving in brand new MacBook

Question

Hi.
I've had my MacBook three days. Whenever I launch Photo Booth, I get a few seconds of motion before the picture freezes. If I get click to another active window and back again, the same thing happens. If I click to take a picture, it takes an image of the frozen frame.
In iMovie I get the same problem: just a few seconds of motion, so it won't record anything.
In iChat I do get continuous motion, but it's really 'choppy', like the breakup of a live TV feed.
So far I've reinstalled QuickTime and Photo Booth, tried a new User Account and used the MacBook via its battery and the mains — but the problem remains. iSight is visible in the System Profiler and everything else works perfectly.
Any thoughts?

Answer 1

Here's my quandary: I bought the MacBook from Amazon, so I'm their customer. Apple told me that as the manufacturers of the hardware, their duty to me is to ensure that it is working correctly under the terms of the warranty, and this would involve either repair or replacement — but it's their call as to which one I get if I take it to them.
If I wanted a definite replacement I would have to send it back to Amazon under the terms of their warranty. In that case, I would run the risk of being charged twice for the computer if something happened to the original on its way back to them.
Is this true? Or can I demand an immediate replacement from an Apple store even if I didn't buy it from them in the first place?