Kolab 3.3 Roundcube via https

[andreas at sektor7g.net]

Hello List,
i am currently banging my head against the wall trying to upgrade 
roundcube to the 3.3 bundled Version on CentOS 6.
Precursor: I temporarily have $config['use_secure_urls'] = false;
My Problem seems to revolve around a misconfiguration of mod_ssl. I 
initially installed kolab und installed the mod_ssl package without 
further configuration. This used to work in 3.1 and 3.2. Now when i 
connect to roundcube via http (non-ssl) everything works fine. When i 
connect to the https version mod_rewrite seems to bail on me. Therefore 
I have no images in rc (and no wallpaper.html).
What is kind of puzzling to me is the following:
The Alias Directive defined in roundcubemail.conf seems to work, i can 
go example.org/roundcubemail and log in, but the mod_rewrite magic a few 
lines down doesn't seem to work. I already installed a test machine with 
Kolab 3.3 and hoping to spot some difference but afaics there is no 
difference, the vanilla setup has the exact same problem. I assume the 
problem lies somewhere in the fact that SSL is a vhost whereas non-ssl 
is a non-virtual host setup.
Any Pointers how to properly set mod_ssl up would be greatly 
appreciated.

regards
Andreas