If you have the 3.708 it may not be worth it to install it again. As i figured there are some changes in the error handling when the video stream starts and in the email configuration.
It looks like it was a firewall problem. I switched off my ESET Smart Security Nod32 Firewall which should have brought up a warning message. I don't know why it didn't do that. But since I switched it off it worked.
I could install the free C-MOR Security as recommended in a virtual box. But what is next? I don't know how to change the IP! How do I do that? The console doesn't accept an input, just refreshes the screen!