Weird sound from my X540 speakers.

Ok, I have the Logitech 5.1 X540 speakers for my PC. I just bought them, and it seems to be working fine except for 1 problem. When matrix is turned off, any thing I do including games, the center speaker will try to make sound, but it comes out all best way I can put it "electric squishy sound". If I turn on Matrix mode, the speakers has good sound, but some sounds are missing. Like in WOW with Matrix on, the casting sound is off, and ventrillo voices can't be heard when people are speaking. With Matrix off, I can hear everything, but like I said, the center speaker makes this weird squishy sound anytime I do something in game to make a sound, like shoot a gun. You can tell you are shooting a gun sorta but it comes out all weird sounding. I thought the speakers were broke but that didn't make sense cause when I have Matrix on, the center speaker sounds clear and normal, but like I said, with it on, some sounds in certain spots are mssing. Can anyone tell me what's going on?

I don't have a soundcard, I'm using my motherboard. It's an nForce 680i. I'm just wandering if the speakers are broke. I don't think they are cause they work in Matrix mode, but it's on non matrix mode that it makes that noise from the center speaker. Microcenter( I bought it from Amazon) told me they don't know what it is, and the speaker migh tbe broke even though it works in Matrix mode.