Thanks folks for the input. As I said, I've gone through three "El Dorado" DVDs, all exhibiting the same freezing up of picture. The first two came from one source within the space of a month and this last one I received just two weeks ago from another source. It may be something in the processing of the product or, as has been suggested, it may be my DVD player. At least with this last copy I was able to get through the movie with only three freeze incidents.
I am going to try the cleaning approach next.
Cheers - Jay