The only problems can come from old installs, most of the time there's a uninstall option, to remove the previous version, or there's not yet a 64bit version app for the new OS, the Apple does not have the typical Windows defragmentation problems, most of the time because of the use of SSD's on Apple products...
btw your BR-DV600U unit has also component video output, capturing from this output would be ideal, this will give a clean & stable video output signal ready to capture, without any TBC. (only if this professional device can play your miniDV recorded tapes) Did you already play
your tapes on the BR-DV600U unit ?
http://pro.jvc.com/prof/attributes/t...&feature_id=02