Sometimes when I first boot up my laptop the back light would turn off on the login screen and I must reboot several times to have the backlight on.

I have an acer aspire 4736z. I installed Ubuntu 12.04 alongside Windows 7. I have noticed some problems: (1) sometimes when I boot into Ubuntu, the backlight goes off after choosing the OS from the Grub and I cannot turn it back on using the button combination for adjusting the brightness. I have to reboot as many times as it takes to make that backlight stay on. It does not happen when I boot into Windows 7; (2) I cannot adjust the screen brightness when using Ubuntu; and (3) the touchpad sometimes works, sometimes it does not. I hope someone would care to help a newbie like me. THANKS!