Well in my case I did locate the problem. I do not know whether this applies to ticket #1723. It is not the application server. Going to a safe video mode my screen does not go black and slowly altering the script for the safe mode I found the line which cause the problem. The boot up hangs (with a blue screen and a cursor) at waitfor_input_server_event_loop_ line When I comment out this line, in the boot script, I get a perfect screen with tracker, icons and all. (But of course the system is unusable. :-) )