Originally Posted by falko
Did you follow the tutorial as close as possible?
Yes, but I skipped step 15 (I din not install Mailman), step 16 (PureFTPd and Quota) and 21 (SquirrelMail).
I am accessing ISPConfig via https.
I did another installation inside a virtual machine and the first error appears during the installation or ISPConfig or immediately after that, when the admin page is accessed.
Since it happened to me on 3 different machines and 2 more people are having the same problem, it might be a bug.
Falko, when you have some time, please take a look at /var/log/apache2/error.log from one of your machines with Ubuntu 12.04 and ISPConfig 3.