I am experiencing this issue also. I can't remember exactly when it started, but I bought my tablet on Aug 2nd and updated to JB within a day or two of its release. I also reported the issue so they can get an idea of the scope of the problem. Here is what I wrote:
I am experiencing the issue with black lines flickering across the screen since the Jelly Bean update. It is especially noticeable on a white background in apps such as Evernote, but happens across many apps. I have been told that others are reporting this issue as well. I am reporting it so that you may know how broad an issue is and respond accordingly.
Others are discussing this problem here: