Why don't you breakup the main movie.
index.html plays "your_movie.swf" frames 0 - 250
contact.html plays "your_movie2.swf" (which are frames 251 - 500)
Understand? Just make multiple movies from your main movie.
There are other ways to do this, like load your movies externally into a main page.
But it is not possible to have a movie "continue" when your button is calling a new html page to load. Which is why I said "load external movies" is a much better way.