From memory. I had to edit some core files to get it to work. It has to do with the procedure not creating a sys user in the database and therefore not being able to create a website. Test the script by creating a dummy user. You should have a new entries in the mysql database for kunde, sys_user & web. More on the issue....
http://www.howtoforge.com/forums/showthread.php?t=14522
Paypal IPN is almost finished and I will release it soon.