I’m sure I’ve heard of something similar to this although I can’t find the link.
I think the problem might be caused by an incompatible third-party QuickTime component interfering with the transfer tool.
You might want to check the contents of the /Library/QuickTime and ~/Library/QuickTime folders (~ represents your home directory) for any non-essential files. In particular anything that’s not part of the normal FCP install might be the culprit.
You can test this by quitting the transfer tool, moving one of the .component files out of that folder, restarting the transfer tool and trying the import again. After repeating this a few times you might find it just starts working and you’ll have found the problem file.
Hope that helps !