Macbook External Speaker Sound Problem

Hey guys,
My 1 yr old white Macbook has a sound problem of the external speakers that i can't find a fix for. It began about a week ago. U can still hear the sound a little bit but it sounds very high, robotic and sort of fake. It is quite hard to hear the sound even when the volume is turned to max but my internal speakers are perfectly normal. Can any1 plz help me?

Thanks

A couple random thoughts...

Make sure it's the MacBook and not the speakers. Plug the speakers into an mp3 player and make sure they work.

Aside from the above, I'm not sure how you would perform a detailed diagnosis of the problem, but I can offer you a $50 fix in the event it turns out to be an internal hardware problem...

I use an external USB sound card with my speakers attached to it. I didn't like plugging in the 1/8" jack everytime I used the MacBook at my desk. I already was plugging in a USB cord attached to a USB hub. So I bought a USB sound card and added it to the hub. Now I have real speakers and all my USB accessories running through a single cord.

I use a Creative Labs Soundblaster USB card. It's $50 from Amazon, Circuit City, Best Buy etc.