Bad case of the sparklies in MJPEG encode

[A.Fenderson]

This M-JPEG encode @ 1024x600 @59.94 fps (http://www.slingfile.com/file/LYDcENDlfD)(72MB, 10-second cut) has got some strange artifact that I'm unfamiliar with, but looks like white sparkles in dark areas. I encoded with the first program I could find that would easily do all the scaling, encoding, and encapsulating that I needed, that being Xvid4PSP, and several other sources I've tried, all at the same quantizer level and down-scaled target encode resolution have worked fine, but they've all also been 30fps or less, though that wouldn't appear to be relevant.

If anyone can give me the proper terminology for this type of artifact, and what the potential causes are, especially any unique or particularly relevant to M-JPEG, that would be very much appreciated. :)

Also, please mention any noob-friendly free M-JPEG encoder software that you find works well for you.

Thanks!