Ok, its fine now. Many thanks.
One second (or third?) problem:
When I try to login as an administrator sitting right at the server (no proxy, firewall or whatever) I´m sent back to the initial page (no login is performed). Nevertheless, this can be overcome in two ways:
1. I repeat the login attempts untill the allowed number is exceeded. I then get an error msg and, when clicking "continue", a regular login as administrator is obtained.
2. After the first frustrated login attempt I change the language...when the new page is called I then find myself logged.
Any hint?
Hope you understood (sorry for the english).
Euclydes