trashing prefs was going to be my big piece of advice…but you did it. have you tried re-capturing or re-rendering the QT file (however it was made in the first place)? i’m guessing that file is corrupted and causing the crash.
personally, i never use QTs in DVD SP4, so i gave it a try after your post. the 3 files i tried imported fine and played back great off the menus in simulation mode, which makes me wonder why i (we?) don’t just use QTs more often when making DVDs. it seems like it would save one step of compression.
any ideas?