I'm not a pro by any means, but since no one else has stepped forward I'll toss a few things out there.
Static is generally caused by some sort of interference, could be a ground issue, could be a cable issue, could be a socket. Something is usually putting juice to the speaker other than the signal its supposed to get, or otherwise affecting its power supply.
So the first thing, is if this is a bigger system that has its own electrical plug, have you plugged anything new into that outlet recently? My speakers always pop if I have something plugged into the same outlet as them and then turn it on or off.
Second is to look at the cables on the speakers, does the left speaker plug into the computer, or into the other speaker? Make sure its plugged in snugly, and that the wire is in good shape.
If you can, try plugging the left speaker into the jack where the right speaker is plugged in. See if you still have static, that will tell you if it has to do with the speaker or cable, or if its something in the jack.
Other than that I'm about out of ideas, not real helpful I suppose. It might be a bad volume control, if we're talking about a know on the speaker also. If its only one speaker though I'd sooner think it has to do with a cable or jack.
Oh yeah. One more idea? Does your computer have different settings for stereo sound? Make sure the speaker is actually playing music/sounds. I helped a buddy hook up a surround sound system and depending on what setting it was on, not all the speakers would play. Those that were just idle, had a little bit of static to them.