Kolab Webadmin

Hi everybody.
One question about kolab-webadmin account access. When the server and my pc 
are in one IP sector I can log in. When I move the server into another network 
segment (routed only or nated, does not matter) I get error message: Internal 
system error! in red stripe when I try login. I use Allow,Deny rules in /etc/
httpd/conf.d/kolab-webadmin.conf at the end of Directory chapter (by apache 
this is better than .htaccess).
When I remove this rules login works properly. I use the same rules at 
roundcubemail.conf and other .conf files and access works as rules are set. 
Only kolab-webadmin.conf file has trouble with them. Is it feature or bug? Can 
someone explain where could be mistake, please? I search log files, but did 
not discover nothing usable in them :( Thank you very much.

Greetings, ladas

P.S. It is the same at all kolab installations which I use.