Well, there doesn't seem to be too many others jumping on this thread and it really isn't my area of expertise, but we'll do what we can.
I think we can eliminate the disks and the burn speed as being part of the problem. When you played the DVD was it on the computer or on a stand alone DVD player? I'm guessing that Corel Studio creates a standard DVD video structure and vob files. lf you put the DVD in the computer DVD drive and click on My Computer and right click the DVD drive and select Explore, do you see a video_ts folder? And if you double click that folder do you see a video_ts.bup, video_ts.ifo and some files with a VOB extension? That will tell you that it's a valid DVD video structure. If you still have the files on your hard drive, the same ones that you burned, you can try playing them with a software video player like VLC or even windows media player. If they do not play smoothly or at all, then something is not right during the creation process and perhaps there are some settings in Corel Studio that need to be changed.