Yes I normaly use an IP adres to connect to my server so that was not the problem.
Anyway, I read somewhere on this forum looking for a solution that it was best to start extracting the ispconfig files and the installation in a place like /tmp.
As I was running my installation from /root and I thougt I could give it a try.
So I removed the /root/ispconfig programm directory and copyied the installation *tar.gz file to the /tmp directory and started the installation again.
And YES this ended with a running ISPconfig system.
Don't know why but it seems to be working now.
Thanks for the support on getting this running!
I am now trying to setup sites and try if everything is stable.