Sorry, I will try to post 2 frame captures - a before and after so to speak - of a video clip so you can see. The lines are basically tiny horizontal breaks in the picture that make everything look very jagged. They appear on anything that has been rendered, that is, after the DVD project has been burned / rendered to an actial DVD-R disc, or to a folder or to an iso file on my hard drive. Whether the final burnt disc is played on a DVD player or computer drive, or whether the iso file or folder files are played on my computer straight from the hard drive, anything that comes out of MyDVD now has the lines. Yes, I have tried shutting down everything during use of MyDVD, in fact I always have.
I have to stress that it used to work fine for a long time and then just started mysteriously one day.
Thanks again fot your help.