To fix "Openbox Syntax Error...."
- cd .config/openbox/
- mv lxde-rc.xml lxde-rc.xml-backup
- restart server
I also have this issue. How does one do that if closing the error dialog box leaves only an arrow cursor on the screen?
I had the same problem and I don't really know what causes it, maybe something to do with the CPU (AMD Athlon x2 250)? or maybe because I have an old 1024x768 monitor? But anyway here is what I did in case someone has the same problem.
As you said, restarting after the screen with the white pixel in the middle, you end up in a black screen with a cursor, just right-click and you will see menu, choose terminal emulator from there and type the commands as told by the other user, then type "sudo reboot" without the quote marks and after that you will end up in a screen similar to that but with a blue background, I don't know if this is how the server is supposed to lock but it's an improvement.
In case the right-click button doesn't work for any reason, click CTRL + ALT + F1, you will be prompted to input your user and password (the one you created when you installed zentyal) if for some reason it doesn't appear, click CTRL + C to close any proccess running on that terminal. The last resort would be CTRL + ALT + F2.
That error doesn't stop you from configuring zentyal, just right-click on the black screen and choose web browser. go to:
https://localhost:8443/ and add the security exception and you will be able to continue with the setup. Adding more packages to your server is not really recommended but can be done from the terminal using the apt-get command.