I've recently been copying my old VHS videos to DVD using a VCR and a Panasonic DVD Recorder (DMR-ES20). Some of them work fine but others have a problem. When I put them in my laptop to play they start out ok but after 5 minutes or so - or if I try to FF - they lock up and the program closes. I called Panasonic and took their advice to switch to a different brand of DVD-Rs but I still have the same problem. These DVDs will play ok on the Panasonic recorder but I really need them to play on my laptop. Any advice? Is this a problem with my laptop's DVD drive or PowerDVD or something else?