[MPlayer-users] DVDNAV fails sometimes?

[Roger Pack]

Hello all.
I notice that with some DVD's mplayer fails to play the DVD (example,
Snow White--I'd be happy to send anybody a legal copy if it would help
with debugging).

http://betterlogic.com/roger/2011/07/mplayer-woe

However, if I then play the thing in VLC (once), then go back to
mplayer, suddenly it plays fine, and from then on.  Anybody have any
ideas what might be happening here?  This is in windows, but I think
I've seen it in OS X before, as well.
Thank you.
-roger-