I was going through the user contributed tutorials (Surfacing, Objects, Populations) and ran into this problem. And yes, I realize the tutorial is rather dated, but new user's are going to run that tutorial and then start searching the site for "lines in clouds" and probably not get to this post and start a new round of questions on the subject.
I'm using v2.0 (build 2.0.3.1) and it's very easy to see. Just add the Power fractal shader v3 and small scale values and there are either render error messages ("An unknown error occurred in trBucketRenderMore() rasterised pass") or vertical lines appear in the atmosphere. The tutorial uses Feature scale = 0.01, Lead-in scale = 0.1, and Smallest scale = 0.001.
It seems Smallest scale values of less than .003 (and leaving the other scales at the default) will initiate problems.
[edit] One of the reasons I bring this up is obviously one could enter a .001 in smallest scale and not get the errors I see now, when that tutorial was written. I would suggest the application limit the smallest value if it can't be fixed in the power fractal shader code.
Oshyan wrote: "I can't reproduce this using the information provided. Was there a specific sequence you made your adjustments in (e.g. Smallest Scale first)?"
All I have to do to see the problem is start tg2, add the power fractal shader, and set the smallest scale to .001 and watch the preview window.