Of course it's slow if Firefox has to open almost 10,000 websites!

Some servers do not respond. Bookmarks Organizer 2.0 will handle this situation and abort the request after 15 seconds so the "Never completed scanning" will be fixed with the next update (to be released this weekend).

> I can't see how to fix errors and delete duplicates.

Just click the "delete" as you can see it in the screenshot.

Please check out the new version in a few days. Thank you.