Originally reported here: http://wordpress.org/support/topic/fatal-error-reported
In your file wp-migrate-db.php the method error() is call sometimes but it does not exists. Only attribute errors (array) is defined.
If any try to migrate any table out of WordPress it fails.
I only tried on version 0.4.3 and 0.4.4.
Can you fixed it please ?
Fatal error method `error` does not exist, fixes #20