Could it be from the widescreen to pan-n-scan conversion? In most cases, each shot in the movie was reframed for 4x3 (instead of just hacking-off the right and left sides). These might be artifacts from whatever process the studio used. And, as none said, they would have been hidden by TV overscan, so Fox probably wasn't concerned.

I may be wrong, but I seem to recall recently seeing something similar during some scene changes on my Star Trek: TMP - Special Longer Version LD...but they were bright orange lines. And, like these, they would have been hidden by the overscan.