login action does not work for any other page than XWiki/XWikiLogin

Using a path like /bin/login/Main/WebHome does not have the expected effect (login). After the submit buton is pushed, the browser is redirected to /bin/login/XWiki/XWikiLogin, without even showing an error message, and the user has to enter the username and password again.

Expected behaviors:
1. The browser is redirected from the first time to XWiki/XWikiLogin
2. The server accepts the login form from any page