definitely make are the players are on V1.22, it says the version number on boot up and in the menu, the link is here for the update if needed: http://pioneerdj.com/support/product.php?c=1467&lang=en&p=CDJ-2000NXS&t=178
download Rekordbox 3.0.2 from the site, don't bother with the RB version that came with the cd players, probably an old disc by now
link for RB: http://rekordbox.com/en/download/
forget serato, link up RB to the players and go to town, no need for serato anymore