I am not sure what is causing this, what come to my mind is that the Shasta rock material is a very old one, been there in the collections since at least Vue3 and surely uses a basic repeater for bump production. Basic repeaters are "fake" fractals, they simply repeat a noise pattern along the geometry, instead of giving infinite detail as true fractals do. So maybe this is the cause of the artifacts. Maybe you should try and edit this basic repeater in the function editor and up the number of repetitions, or change it for a simple fractal and edit this fractal. Of course this means fiddling in the function editor, but it may be the cause of your problem.
You could also try enabling texture AA instead of changing the noise, but be sure to uncheck "recompute subrays", this option will take forever to render and is only useful on reflective/transparent materials, and only in very few cases.
You say you edit your animation to DVD, so I assume you are using an mpeg2 compression? What if you output to a non compressed format? Do you still see artifacts?
Also, have you tried a non compressed image format for your single frames? I know png is supposed to be lossless, but how about trying tiff or tga, so you are 100% sure png isn't the culprit?