the import doesn't finish

I’m transferring my blog from wordpress.com to wordpress.org, but when I want to import all the posts etc. from my export file, it doesn’t work anymore at the moment where I’ve selected the author. I click on ‘submit’ and I wait (long) and there isn’t anything happening. (Well there is, I see that it’s loading, but after 3 minutes that stops!) I’ve tried it a lot of times, does anybody knows what I’m doing wrong with the author-part?