Reply to S4 50-60 Hz hum and traktor searching issues

Hi Guys,

I just bought a pair of powered speakers and I'm getting a terrible hum when i use my S4 with my macbook pro.I have a pro900 powercenter by monster cable and have my s4 grounded to it,including my denon mixer.I run the S4 through the misxer because i have another dj setup by denon, but the mixer too is grounded.I even went straight from the S4 to the powered monitors and still a hum.The hum would get lower if i used the mac on battery power but thats not useful in live situations.I'm using a regular usb cable but have read about shielded cables.Should i try that? Anyone use Hum-X also?
My other issue and way more annoying is searching for a song in traktor (say i search for "Show me Love") i get multiple results which is fine because i have various versions, but i also get duplicate results and when i try to load some of them they dont load as if they werent on the drive.I dont use playlists.all of my music is on my internal drive and on the root of the drive so i go to explorer to find my music folder.i know i have 5 versions of the song so why do i get more than five results??? How can i clear this up? If anyone has any advice i'd appreciate it.

Thx!