Different passwords after Gallery2 Drupal user import/synch.

I've spent days trying to get my gallery users imported into a new Drupal install.
I have managed to get all my gallery users into Drupal but about 25% of them are reported by gallery module user status as: Imported/Different hash method,Different Passwords

I've tried logging into Drupal with one of the affected usernames and the password is not recognized - it is also no longer recognized by standalone gallery.

Password retrieval/reset in Drupal works well enough for individual users - but I am puzzled as to why some passwords are accepted for the synch process but others are not.

Anybody know what's going on here?