ATV streaming video at wrong speed

Hey guys

having an issue with my ATV2 which i've actually noticed happening on a few different videos.

i used Handbrake to convert a bunch of film clips. when i put them in iTunes and play them back on my computer they're played back at the correct speed and hence with the audio at the correct pitch.

when i play them back from my Apple TV however, some of them are playing back at a faster rate and with the audio at a higher pitch. i've also noticed this same thing happen before on various video files. all of these files were converted in Handbrake during the same session using the same preset designed to work with Apple TV and aside from these few instances, i've never had a problem.

so quickly: some (seemingly random) video files playback correctly in iTunes but too fast on Apple TV.

does anyone know why this would be and/or how to fix it?