[phpGroupWare-users] Installation worked but then blank page

[Anders]

OS: mandriva 2006
phpgroupware: 0.9.16.011
apache: 2.0.54
php: 5.0.4 (I've recently used the ini_set('zend.ze1_compatibility_mode', '1'); 
mod in phpgroupware/header.inc.php without any change regarding to the problem 
below

I installed phpgw and being sort of a newbie I finally made it work, logged in 
and started looking around. Since one of the major reasons I'm looking into 
groupware is to be able to manage projects and sharing documents within those 
projects I immediately started out trying to implement this solution 
http://docs.phpgroupware.org/html/install/apps.html
I setup a new account to use for testing and after logging out from admin 
account I could no longer login, after klicking "login" all was white.
I have not changed anything in apache, php or mysql.
http://www.sko.miun.se/anders/httpd_errorlog.txt you can see my httpd_errorlog 
if it can be of use.

I'm not skilled enough to interpret the errorlog by myself so any help would be 
appreciated. 
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