Distorted sounds

Is it just me?
All sound in SL is distorted, since the weekend - sounds like I'm surrounded by daleks when people speak. It's happening on all sounds... waves, objects, music, voice chat. And it's only SL, too. Streaming music and movies are all fine on the pc, even whilst SL's running.
It happens on both regular and release clients. I've changed headsets, used different usb slots, checked for crap on the pc, reset the modem a few times, all to no avail. Even cleared my cache, for the fun of it. And, no, I didn't fiddle with anything on my pc, before this happened.

It doesn't make for a pleasurable listening experience, I must admit. Any suggestions?

I get a similar effect - sound is fine except in SL where is can distort and crackle. CDs, DVD's all play great - sound from other applications all seems ok. Just SL that has poor sound quality. I re-installed sound card drivers and checked device working ok and everything.