It could be a problem with your process of copying the commercial dvd. I recommend getting DVDFab HD Decrypter, which is the free section of DVDFab. It will continue to function even after the trial for the main part of DVDFab expires. Use this program to rip the dvd to the hard drive. This will insure that you have removed encryption correctly.
http://www.dvdfab.com/free.htm From your description, this movie fits onto a blank single layer dvd without compression, but if you need to compress, you can use a free program called DVDShrink.
Then burn to a disk. I personally use ImgBurn, but Roxio should work for this. Use high quality disks, like Verbatim 16x and burn at moderate speed...8x or 12x.
If you want to use RW disks, I'd suggest Verbatim +RW variety.