[horde] Infinite loop in login

[Frito Lay]

Hello list,

I'm trying to install horde 3.3.4 in a linux machine, distro is suse 11.

Apache and php configuration is the standard one, there are no strange redirects, rewrites, etc configured.
I have followed each step closely, there are no missing requirements

Whenever I try to log in for the first time, I get an infinite loop:
index.php -> login.php -> index.php ...

I think the problem is index.php thinks I'm not authenticated, while login.php does.

If I comment this section in login.php:

/* Try transparent authentication. */
if (Auth::isAuthenticated()) {
    require HORDE_BASE . '/index.php';
    exit;
}

The loop breaks, but of course the application doesn't work.

I have read similar reports by people installing horde in the webroot.
For me it doesn't make any difference, I get the same behavior by using webroot='', or webroot='horde'.

I have installed previous versions of horde in the past, even written modules using the framework, and never came across this one before.

Any ideas?