[horde] Refresh Problem

[hricisin at inmail.sk]

Hello,
I am administrating horde on my server. 
I am very satisfied with horde and all "plugins" that I have installed.
But there is one problem, that I can not fix. When I press refresh in my browser, horde 
navigate me to the login page. I am using bottom frame as horde menu.
You can try it on http://mail.bart.sk, login: test, password: test.

Server configuration:
Webserver: Apache 2.0
PHP 4.3.4
Maybe you found usefull session settings:
session_autostart = Off
session_use_cookies = on

Thanks for your reply.
Bye, Michal Hricisin