If you mean you used the “make your own dvd video” option, that should have worked. To help test if it converted wrong or if it is a burning/disk issue, convert it to hard disk first. Do the same as before, but instead of selecting your burner as the destination, select a hard drive folder. Then open nero showtime. Click the little folder icon to the top left of the play button. Select play from folder, and find the folder you converted to. If the dvd structure is correct, it should play fine. If the dvd structure is wrong, it should give an error about not being a compliant dvd video, and suggest using the media files option to play.
If it is correct, you can investigate issues with your drive or media. If it isn’t, you can look into nero settings to see where the problem is (default settings usally work though).
Fyi, it doesn’t take an hour and a half to burn. It takes most of that time to convert the video files. Once you have done it to your hard drive, you can use nero recode (copy entire dvd video option in start smart) to burn in 15 minutes or less. If it is drive or media issues, it would be good to work from a converted movie any way so you don’t have to wait 1.5 hours each time till you find the problem.