Ok, I found the screen size setting on the DVD player. You are right, it was set to 4:3, and setting it to 16:9 corrected the problem. THANK YOU!
Why did professional DVDs play fine for the last year I have had this TV and DVD player? My concern is that I will be sending my DVDs to people who know much less about video than I do, and I couldn’t even figure out this problem without your help. Is there a way to make this DVD “fool proof”?