I checked off course the cronjobs, and everything seemed ok. I already knew that I had to wait one day or so (cronjeb webalizer runs about 4-and a little more minutes am) and I did that.
But is still is strange that with 3 different os-ses the same problem appear. With the perfect installs everything is strait-forward and also ISPConfig installs smooth.
The onley modification I made within the perfect install is a different IPAdress and another hostname / domainname. With this everything is running fine (www, ftp, dns etc.) except webalizer.
Could this have something to do with the modifications ISPConfig makes within the cronjobs?