Uhmm... as far as I remember, you can easily change the region code of the DVD Player app once you insert a DVD from another region than the one already set, but that's limited to five changes until it's locked, so maybe you already changed it too often. I've seen posts claiming that VLC doesn't care about the region code, though I can't test this right now
I have about 45%/45%/10% split of different DVD regions in my collection, so then I have to go on extended periods of time just watching movies from a particular region before I change back to another one. So doesn't exactly last in the long run...
I heard about the VLC thing, but it allegedly doesn't work anymore as far as I've understood. Plus the playback quality apparently sucks judging by several posts to other forums and blogs.
Either way, the point is that it was a lot easier on Windows: just downloaded this little application, and it was region free ever since.
Apparently the dvd drive that Apple uses is particularly tricky or something if I understand it correctly. Because to make it region free, you have to make the DVD drive itself region free, but also OS X. Ironically enough, if you install Windows on your Mac you can more easily make it region free. But I don't have a Windows copy so...
And getting an external DVD drive, true, but I don't want any more gizmos to carry around.
So I'll just continue downloading torrents of movies I already own, and continue to be happy with my Mac despite this little annoyancem
Edit:
Found the below text explaining some of the difficulty:
the problem with the late power-/i- and new macbooks is that they contain recent brands of matsushita (read: panasonic) dvd drives. those have a really nasty “feature” in their firmware that does an additional comparison of the dvd and drive regions. in case they don’t match, you only get errors out instead of data.
unfortunately, to day, no one has gotten his hands on original firmware to hack and make the drives usable.
the only solution seems to be pulling out the firmware stored on a drive itself and working with that - but noone has undertaken that task yet.