Right after the 0.9.7 release of gecko-mediaplayer I was made aware of the fact the apple.com/trailers videos don't work anymore. They worked about a week ago, but Apple apparently made a change. A bug was opened in the gecko-mediaplayer bug tracker (#34). And due to the information provided on how to work around this bug, I was able to create a patch for this bug.
SVN now has a fix for it and should work correctly. Depending on demand I may do a new release of gecko-mediaplayer.
EDIT: Sept 23,2009. I made a similar patch to mplayerplug-in and the code is in CVS now, or you can get it from the nightly code build on the 24th.