QT Pro convert .MP4 to .MOV

I'm trying to get QT PRO (7.5.5) to convert a .MP4 file (H.264 format) to a .MOV file. The source is a 15 second video created from Sony Vegas 8.0c using their Sony AVC encoder. This is 1080p (24fps).

The .MP4 file plays great in QT (my client still wants the file as a .MOV rather than as an .MP4).

In QTPro I load the .MP4 file and then do a "Export". I choose "Movie to Quicktime Movie". Checking the format has H.264 selected. The resulting .MOV file is very small (like 8KB verses the 8MB input file). And.... the MOV file is 15 seconds of nothing!! 😟

Any ideas on what is going wrong?

Thanks

-Liam