maybe its because of you configured a hostname and your testing with :
http://localhost/webapp or http://IP-Adress/webapp.
run apache2ctl -S to have a look at your apache config.
and tail -f *.log in the apache webfolder then try again.
I think you hitting a vhost misconfiguration and you request is ending up in a unconfigured vhost. aka the ip default.
I made this script (below) on debian but you can adopt it for sles.
basicly it does the follow, for every ip create a ip vhost. then create a namebase host of the previous ip host.
You should see something like this in the end, ( localhost as example )
127.0.0.1:80 is a NameVirtualHost
default server 127.0.0.1 (/etc/apache2/sites-enabled/000-localhost.conf:2)
port 80 namevhost 127.0.0.1 (/etc/apache2/sites-enabled/000-localhost.conf:2)
port 80 namevhost 127.0.0.1 (/etc/apache2/sites-enabled/000-localhost.conf:19)
i hope this helps a bit in finding your problem.