I think you may have it Qob'nuH. It sounds like what he is describing.
Go to the preference button in the upper left display (it looks like a little PC)
and left click on it.
At the top left of that display (MFD) is a button that looks like a checkboard
in the upper left hand corner, click on it and see if the lines go away.
If this doesn't help, let us know your vid card and driver version please.
Thanks,
Dave