This is probably a problem with the media you are using. Slowing down the burn speed might help, but I think you would be better off using Verbatim 16x media. And I’d try burning it at 12x or 8x.
My Samsung 203B burns Verbatim +R 16x very well at 8x.
Memorex varies greatly in quality, ranging from mediocre to poor. They use different suppliers, so it is hard to know exactly what disks you will get…and they seem to get less than the best disks available from those suppliers anyway.
Your copy program is one that I am not familiar with. Does this rip and compress the movie to fit onto a single layer dvd? It might be part of the problem. If you continue to have freezes and skipping, even after changing the media to Verbatim and slowing down the burning speed, this program is next on the list of suspects.
There are free tools that are highly recommended around here if you care to look at them, including the regularly updated free decryption program DVDFab HD Decrypter, the compression program DVDShrink, and the free burning program called ImgBurn.