Black bar in the centre of the screen

I used NERO to make a compilation of a bunch of videos and when i play them back there is this strange little black rectangle that is centred about 2/3 of the way down the screen and is about 2/3 of the width of the screen.

Help!
Thank you.

Thats a new one :eek:

Can you attach a screen dump so we can see exactly what your taking about.