user accounts

Alright, so i install gallery, looks good, i can logon with my admin account and modify things, very good. I can upload pictures, still good.
I make a new user, it sends me confirmation email, cool so far, i click on the link to make a password and i get

Make New Password
Error: Not a valid username
Enter the Gallery

that screen, the user was not saved, check to make sure with admin account, no users except admin.
Now - /i can/ create a new user with the user management screen, and it saves fine, sends out confirmation email, etc etc

And i see nobody else has this problem, so i'm sure i've messed up something, anyone know what i did wrong?

(I want people to be able to add themselves without me needing to do it)

(Edit: i have tried out the sessions test page in the config wizard, and it did indeed work properly - in case someone asks)

system information:
Gallery URL: http://chaa.no-ip.org/phpbb2/gallery/index.php
Gallery version: 1.5
Apache version: 2.0.54
PHP version: 4.3.11
Graphics Toolkit: NetPBM
Operating system: windows xp professional sp2
Web browser/version: IE 6.0.2900.2180.xpsp_sp2_gdr.050301-1519