I had similar problems exporting from the XDCam EX CODEC sequence to QuickTime movie. I needed to do this for a multiclip edit. UntilI filled the gaps in the sequence with colourbars the export would hang at the beginning and end of clips. The export for a very ling sequence was taking over 3o hours on MBP. Once the gaps in the timeline was filled, export took less than 30 minutes. Cheers David Salomon.