Original and Rip DVD Movies (Need Help)

I have an LG DRD-8160B DVD Rom drive and no mather what kind of dvd movie I play (original or copy) my WinDVD Platinum will stop playing after about 35min. I get perfect sound and picture but after the 35-40 min the picture freezes and I am force to close the program. I don’t think is the software because I have tryied Power DVD4 for XP as well with no luck.
Can someone have any sugestion on how I can overcome this so I can finaly whach the end of all this films.

I have an ASUS A7V8X Raid with Athlon XP 1700+, 384Mb DDR and 64Mb Ram Graphic card running Win XP Pro. :confused: