In a thread that dates back to three months ago on the WordPress.org support forums, users are again reporting that when trying to import content from Blogger into WordPress using Bloggers authentication method, they receive an AuthSub Token error and are unable to continue with the import process. However, thanks to some quick actions on the part of the WordPress.com support team, WordPress.com users are able to import from blogger just fine using the authentication method but WordPress.org users are still stuck in the dark.
One solution that has been published which appears to be working for a number of people is a service called BloggerToWP.com which links to a plugin called Blogger Importer. The secondary solution offered is a specific URL called Blogger2WordPress.appspot.com which contains a form where you upload your Blogger export file and it will be translated into a WordPress XML WXR file. However, due to PHP configurations on shared hosting servers, folks have been running into the issue of the XML file being too large to import since most hosts only allow 2MB files to be uploaded. If you fall into this group, I suggest you send a trouble ticket to your web host to temporarily have that limit increased until your import has completed.
Actually, it looks like there’s a simple change that needs to be made to fix it.
Related info:
http://core.trac.wordpress.org/ticket/14566
http://core.trac.wordpress.org/ticket/14629