Probably not sheilded right.
Have you tried plugging into the back panel connectors?
I don't think a card will help, as you stated, its not your mobo, so why waste money on a card when the problems connectors.
My mic/headset has a 10ft cable o I plug into the back panel.
Foldie = i7 950@ 4.0Ghz Gigabyte x58a-ud3r EVGA 970 SC Corsair H100 Corsair hx520 3x2gb OCZ Gold Corsair 650D
Woohoo = L5639 @3.1Ghz EVGA SR-2 gtx 260-216 Hyper 212+ Corsair 1050hx 6x2gb Corsair XMS3 Blackhawk Ulra
Alienware 18 - SLI 770M 4700mq 16Gig