All of a sudden I'm seeing blue vertical lines in the preview windows, for a clip I've been working on for some time. These just appeared, and don't seem to actually be in the source material (an avi file which I viewed in another app).
I'm attaching a screenshot to illustrate.
Nvidia graphics card? Set the 3D settings to "Let the application decide" and the lines will disappear.
Jeff, that did it! Thanks very much for your quick help on this, I really appreciate it.