I'm opening a new thread, similar to solved one:
as I'm not the author and it doesn't work for me.
When I boot my Toshiba satellite, I can hear the login bongos play, but can only see a black screen with my mouse cursor. I tried to put GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux acpi_backlight=vendor" in grub, but it worked only once.
There is a strange thing : if I force the grub menu to display on boot, then choose "ubuntu" line, everything goes fine. So what is the difference ? There must be one as I have a black screen in a case, not in the other.
And I don't know why this error appeared suddenly.
Thanks everyone. Have a good day.
PS : my ubuntu is 13.04 with last updates (I suspect one of theses updates to be responsible).