Migrating from wordpress.com to hosted wordpress 3.5.1

So I’m trying to migrate my sister’s wordpress.com blog to a hosted instance of wordpress 3.5.1. The export of the .xml goes fine, but when I try to import it to the hosted version I get this error:

Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, webmaster and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

I’ve tried re-installing wordpress, using different types of exports (just posts etc) with no luck. Any help would be appreciated.