I have an Acer Aspire 4736 Laptop running ubuntu 10.10. I recently used update manager to upgrade to 11.04. After upgrading and rebooting, I had a problem with the following symptoms: Acer's BIOS Splash screen showed up followed by GRUB OS selection menu. After that the laptop's screen turned purple and then blank. A few seconds later I could hear the welcome sound but the laptop screen was blank. I connected an external monitor via HDMI and the image came up on the external monitor And so I scoured the net and came across this forum thread and realise that my laptop's LCD panel was showing an image alright but the backlight was off - confirmed this by squinting closely at my laptop's LCD panel. I followed unknown47's advice and restarted and it worked. If you have an Acer Aspire laptop and have a similar problem, do this: Bootup ubuntu. Connect external monitor. Edit /etc/rc.local and add before exit 0 : setpci -s 00:02.0 F4.B=00 Edit /e