Posting for a friend:

My friend has a Panasonic 42inch plasma display and only has regular cable (not digital).
While watching certain channels, she sees lines in her screen. Other channels are fine. She can watch the same program on two different channels, and one will have lines while the other won't.

I have asked her to change the wires coming from the wall to see if that makes a difference.

Any other suggestions?

If she is getting lines on one channel and none on another, those lines are coming to her from her cable company.

A 42" Panasonic deserves satellite...she can either call the cable co. who may or may not be able to fix the problem, or go to Bell.