[WPG2] Validation Problem

Hi there. Searchfunktion wasn´t working. Google dind´t help.

Gallery version (not just "2"): 2.1.2
PHP version (e.g. 4.3.11): donno
PHPInfo Link (see FAQ): donno
Webserver (e.g. Apache 1.3.33): donno
Database (e.g. MySql 4.0.11): donno
Activated toolkits (e.g. NetPbm, GD):
Operating system (e.g. Linux): Linux
Browser (e.g. Firefox 1.0): FF 2.0

When I try to install WPG2, I get a Validation Problem.

I type the Gallery2 URL: and klick "Auto configure". After that I get a Message:

Warning: Cannot modify header information - headers already sent by (output started at /var/***/***/***/***/***/wp-admin/admin-header.php:16) in /var/***/***/***/***/***/wp-includes/functions.php on line 2481

I can choose No or Yes. If no, it returns to The wp-wpg2 plugin page. If Yes I get a white page with nothing on. I can´t mark anything, it´s just white.

Ever heard of it?