I actually had the same problem. Is it just on cold starts that it makes the noise and then goes away right away? if so, the problem probably lies in the bendix gear within the starter. If you had the starter changed two years ago, it probably had a warranty. Either get your starter rebuilt with new bendix or replace it entirely (bring your core). hope this helps. when you change it, check for damaged flywheel teeth as well.
This thread could be helpful as well...check it out.
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=trouble&Number=1032261&Forum=trouble&Words=starter&Match=Entire%20Phrase&Searchpage=1&Limit=25&Old=1month&Main=1030584&Search=true#Post1032261 
