[horde] unsuccessful login after horde installation, 2 auth methods tried

[Tonio]

Hello all,

I'm trying to install Horde 3.1.4 on a Debian Etch server.

I have done the first step of the install howto, and the page
http://servername.com/horde/test.php doesn't show any red, blocking
lines. I ran the MySQL script, the Horde database and user are created.
When I connect to the page http://servername.com/horde page, the Horde
administration page shows up (logged in as Administrator without
password, as said in the manual), and I start configuring the tabs,
especially the ones asking the database backend (MySQL).

1. In the Authentication tab, I use the FTP Authentication, I put
"antonio" in the list users with admin rights. Then, I save the
configuration, and I come on the login page. If I login with a wrong
username/passwd, I get a message stating the error. If I give in the
correct antonio/mypassword, the login information is sent to the server,
which sends back the login page with blank fields. The authentication
works, as the logs of the ftp server are showing, but I can't get in the
Horde admin page.

2. When I use Automatic authentication, which whichever username (also
entered in the admin-allowed users' field), and when I save the
configuration, then my browser appears to wait for a response from the
server, indefinitely, and the page stays blank. When looking at the
apache logs, I see an endless loop of those four http requests:

"GET /horde/login.php?frameset_loaded=1 HTTP/1.1" 302 26
"http://servername/horde/login.php?url=%2Fhorde%2Fadmin%2Fsetup%2Findex.php%3FHorde%3D4204df68871c0243c7565b562b49406b&nosidebar=1"
 "GET /horde/login.php HTTP/1.1" and referer
"GET
/horde/login.php?url=%2Fhorde%2Fservices%2Fportal%2Fsidebar.php&nosidebar=1
HTTP/1.1" and referer
"GET /horde/services/portal/sidebar.php HTTP/1.1" and referer

Do you have an idea of what happens in both cases, and why I can't get
to the Horde administration page?
I didn't try any another authentication method, but I think the FTP one
works, and the problem comes from an Horde php scripts, what do you think?

Many thanks in advance for your answers!
Antonio