I have the Logitech z-640 surround sound speakers and I get no sound out of the back two speakers, but the 2 front ones, central and sub woofer works fine. And when I connect it to my television for my xbox 360 it works fine only when connected to the computer it doesn't work. (in advanced audio properties I have it set to 5.1 surround sound speakers) can anyone help me. Oh and I have creative sound blaster live! 24-bit sound card.