Ok so I searched some more and stumbled upon this : http://www.youtube.com/watch?v=IJH1mSV3A-Q
This seems to be the exact problem I am having. Seems to be related to a faulty fan controller. Looks like I'll be contacting NZXT customer service. I heard they are not the best. Any truth?
In the meantime before I get my replacement, maybe I can plug my new fans into the motherboard and that will eliminate the noise? Because before I installed the new fans it was working OK on medium. Could there be a conflict between the NZXT fan controller and my Cooler Master SickleFlow fans?