if tha playback speed the movie is changed, the playback of the sound is also changed... so the pitch changes! Using the playback rate value, you can calculate the pitch shifting that is done, and un-done it with a pitch-shifter?? this would probably decrease the sounds quality.... but you could try it, max has a pitch shifter ready in one of it's examples!
you can do the pitch-shifting, but you need the audio as an MSP signal. playing directly from jit.qt.movie it's not a signal, it's played by QT and isn't really controllable aside from volume (and maybe some other things, but not pitch-shifting). Use [spigot~] to grab the audio as a signal, then look to gizmo~ for pitch-shifting. Use the reciprocal of your movie rate to determine the pitch transposition by going through [!/ 1.]
So if your movie rate is 1.5, going through [!/ 1.] is the same as
1 / 1.5
which gives 0.66667
That value into gizmo~ as your transposition amount should pitch-shift the audio back to "normal" (though there are always artifacts...try different pfft~ sizes to suit).