I have this problem and was wondering if I had a problem with my camera and what it could be. I have a virtually new canon xm2 and have been recording some recent footage. When I capture it in my Liquid Edition NLE, the footage for some reason has a flickering horizontal line on the upper-most part of the footage. What could this be from? I wonder if its my camera, or if it's my NLE?
I really wouldn't worry about it too much. It would be hard to tell whether it's the camera or your NLE unless you're willing to do a little test, such as to connect another camera to your computer to see if the problem continues or goes away. Don't forget that you're viewing the underscanned video image anyway and that the flickering line will never be seen on your final product.