Comment 13 for bug 104535

Finally, i solved it on my dell studio 1555. First, gksudo gedit /boot/grub/menu.lst. And edit it by adding 'noapic' without quotes at the end of the boot loader entry for the os, after 'ro quiet splash'. Then, run sudo update-grub. Then, edit /etc/laptop-mode.conf and change enable_laptop_mode_on_battery to 0. Then, edit all files of the form, /etc/acpi/*.d/90-hdparm.sh, and replace the line following if ["$State"="battery"] then;
hdparm -B 254 $dev
Else
hdparm -B 254 $dev. Thats all.. The noapic solves the dell studio ubuntu problem of not recognizing ac adapter, no changing brightness, closing lid lcd switch off, and elect key. Try it and let me know!