OK I managed this, thanks.
If I enable SSL on two webs at the same time, I got still this error, if I start apache2:
* Restarting web server apache2 [Sun Nov 20 17:40:45 2011] [warn] _default_ VirtualHost overlap on port 443, the first has precedence
... waiting [Sun Nov 20 17:40:47 2011] [warn] _default_ VirtualHost overlap on port 443, the first has precedence
[ OK ]
When I try to access the webs by https I got always the cert from the first enabled SSL web and it redirects me always to that web.
In the vhost-file there is configured a virtual host on *:443 and the paths to the certs of the corresponding web are correct set.
apache2 and openssl Version are SNI capable. My browser too (Firefox Vers. 3.6.24 for Ubuntu)
I don't get it. What I'm doing wrong?