I know you've obviously spent a lot of time trying to get this to work but maybe taking your old VHS movies to a professional to get them concerted might be a better option?
it doesn't seem like a problem that can fix itself so outsourcing seems like a reasonable suggestion, it's not too pricey and you'll have your files converted problem free and reasonably fast
if you need recommendations I'd be more than happy to help, I know video to dvd transfers, Brighton (supaphoto.com) offers this service
hope this helps :)