I can not login my site via mobile joomla! 0.9.11.

Case 1:Firefox and Useragent Switcher
I try to login, l can do it.

Case 2:i-mode mobile simulator II
www.nttdocomo.co.jp/binary/archive/service/imode/make/content/browser/html/tool2/download/imodehtmlsimII_840.zip

simulate mode < 8:
"無効なデータを受信しました(303)" returns, so I can't(Japanese Error message).
"syntax error(303)" returns, so I can't(English Error message).

simulate mode = 8:
l can do it.

Case 3: SO902i(SONY Ericsson)
"無効なデータを受信しました(303)" returns, so I can't(Japanese Error message).
"syntax error(303)" returns, so I can't(English Error message).

These cases are happened on this Mobile Joomla! site, too.
I heared that some i-mode mobilephone not support relative-url

My site's configuration;
PHP built On: Linux
MySQL: 5.1.53
Language: utf8_general_ci
PHP: 5.2.154
Server: Apache/2.2.3 (CentOS)
PHP Interface: apache2handler
Joomla! 1.5.22 Stable [ senu takaa ama woi ] 04-November-2010 18:00 GMT
Themes: rhuk_milkyway

Anyone please try my site?
url: jm.gressaude.com
username:demo
password:password

After login Joomla redirects user with 303-redirect header, and most likely old imodes consider it as "syntax error". But I'm not sure and will look at the issue later.

PS. Are old imode devices still popular in Japan? It seems that most of modern devices support XHTML (andeven HTML5) markup.