User management in Mambo embedded Gallery

I'm having a weird problem with user management.

Generally, it's fine. I can set user permissions for albums etc.

But when I click on the gallery page admin (from within embedded gallery in mambo or going directly through gallery) the user list I get is completely wrong. Generally, this wouldn't be a problem, but I'm trying to assign admin rights to one of my users and I can't!

Where are users stored? Is there a way I can just manally make the change?

I'm running Gallery 1.5 RC2 embedded in Mambo 4.5.2.1