hi. i am trying my sound blaster live! 5.1 sound card and i have an ATP4 altec lansing speakers ( 4 sats + 1 sub ). when checking it only the right and left front speakers sounds. only a humming sound from the rear ( you know that it's on ). i tried changing the setup and it tested " front right, front left, rear right and rear left" BUT the "rear left and rear right" sounded from the 2 front speakers and no sound came out from the rear speakers. how can solve this? thanks a lot.