Audio killing framerate

Despite being in in the corner of a sandbox I was getting a very jerky framerate which according to timers was being caused by... audio. Second Life isn't multithreaded so it makes sense that a slowdown in audio processing would kill framerate but I don't see why there is any audio processing as I don't have sound enabled!

By the time I took this screenshot the value had decreased a lot from what it was and then it eventually flattened out.

http://imagesocket.com/view/audio6bb.jpg

Seen this to been awhile now tho, not a clue why it happend but it was the same audio killed my fps.

Havnt seen it since i switched to sblive and audigy4 on the pc's.