Such unnecessary grief! Who comes up with this bs? "Hey, I think I'll just make life harder and more complicated for everyone by making my hardware not play the normal software...no, no, no....they'll have to jump through hoops to do something simple like play a DVD."
Anyway...I hope you can pick-up on my own personal frustration with this problem.
If you want to go from PAL to NTSC, than you are going to need to "interlace" the DVD, making up for missing data. I can't explain it totally, but you'll either add frames/second or extra-data per frame.
Thus, I haven't figured out the problem totally, but you need JES Deinterlacer, MPEG Streamclip (w/ MPEG 2 ability), and Quicktime Pro.
There are more simpler programs for PC that do it all, but there is nothing for Mac.......YET!