This suggestion I have seen is to try to identify the image that stalls the transfer, and remove that image from the transfer process.
That makes kind of sense. Question is: how can I identify the relevant photo?
I don't know anything about the converter because I'm not a Mac user. But if that converter is moving the images somewhere, or if you can watch a list of converted files during the conversion process, that would be the only way. Sorry, but since I'm not a Mac user I can't be of any more help to you.
how can I identify the relevant photo?
Is it possible to use a "divide and conquor" approach, for example do 1/10 of your files at first, then if that goes well, another tenth..
Have you repaired permissions and repaired your Aperture library?
Some folks are having issues with foreign character sets in project and image names.
There's a ~\Documents\LibraryImport.txt and ~\Documents\LibraryImporter.log that is created that may give you some clues.