[horde] login.php redirects to wrong directory?

[ossipetz]

Hallo

this is my first horde/imp installation, so please be patient :)

i follwod the install document to install horde (as first step)

the test.php works fine (http://horde.monis.ch/horde/test.php)
but when i try to go to the login page at: http://horde.monis.ch/horde/

there is a page not found error: The requested URL 
/horde.org/horde/login.php was not found on this server.

/horde.org/ is the directory name where the files are located: 
/wwwroot/_webapp/htdocs/horde.org/horde
(path here i installed horde)

i really dont get what i am doing wrong... its probably something stupid 
but i can't find the mistake in my configs :-/


any suggestions and hints are highly welcome!
thanks a lot :)

ossi