I could not boot my laptop without external monitor connected to D-Sub interface.
After choosing OS in grub the screen became black but nothing else happened, no harddisk activity. It seemed there was problem with splash screen initialization. I wanted to turn it off but it was impossible to even boot to rescue mode.
Final solution was done in two steps
Change the boot loader settings.
Store boot settings permanently after successfull boot.
Change your boot loader settings
If you are using grub choose your operating system and press "e" for editing. Then find line beginning with "kernel" or "linux", press "end" and delete options "quiet splash". Press Ctrl+x. Your system should boot correctly without graphical splash screen.
Save your settings permanently
For smooth start you should save your settings to grub configuration. Open file /boot/grub/menu.lst or /etc/default/grub AND /etc/grub/grub.cfg - depending on your grub version and disable splash screen:
For grub version 1 open /etc/grub/menu.lst and delete all words "splash"
For grub version 2 open /etc/grub/grub.cfg and delete option "splash" from option GRUB_CMDLINE_LINUX_DEFAULT. Then open /etc/grub/grub.cfg and delete word "splash" from your boot profile.