Apple is replacing original MacBook Pro motherboards with a new revision which solves the ‘whining’ problem, according to a reader report at Macintouch.
One Apple customer has posted the letter (73k jpeg) he received from AppleCare, which notes that OS X 10.4.6 was installed on MBPs which were still running 10.4.5. It appears the newly-revised motherboards require at least 10.4.6.