Ok, I will first explain exactly what I did to make the DVD here.
1.Started with 2 .avi files of considerable size, 2 parts of one movie.
2.Converted each file separately into the MPEG-2 DVD format using TmpegEnc using the method specified here on vcdhelp
3.Used Ulead DVD Factory to author DVD, just put one of the Mpegs after the other in correct order.
4.Tried burning with Ulead, and tried exporting the DVD Folders and burning with Nero.

In both cases the audio ended up being out of sync from the video when I played the DVD on both my computer and a standalone. The Mpegs are not messed up, they play flawlessly on the PC, I tested before I authored/burned and then again after I ran into the problems.
Any help is greatly apreciated.
Thanks all