Black line at the top of screen? What is it??

[Magnavox300]

I have been enjoying my new Magnavox 21" B&W,
thanks to everyones help here.

A new black line, with some white dashes just appeared at the top of the screen when I am watching DVD's.
Tried the Vertical Hold at the top of the set,
and right before it dissapears, the vertical goes out of sync.
I tried adjusting the vertical height at the bottom of the set,
and I can get rid of it, but then a white glare comes up from the bottom!
Any ideas?
Thanks!

Magnavox300