The most common problem
with these is a disc error. It requires some minute adjustment on the
laser. Not too complicated but you can trash a unit if your not careful.
The instructions for this can also be found on the internet.

It must be noted that this is not a surefire way of fixing this problem.

According to a Nintendo certified tech that I talked with at a local repair
shop, this is primarily due to design fault in the disc drive.

At the risk of using a cliche, tweaks and adjustments will only delay the
inevitable.
I still recommend calling Nintendo and seeing if they will grant an extension
of the warranty so you can ship the console off to them for an exchange for
free. You get a reconditioned console instead of tinkering around with a
console that may be on its way out. - Reinhart