Hi, I hope this is the appropriate forum. This is a hardware issue but I'm betting the solution will end up being a software one
I have a Dell Insprion 600m laptop. I dual boot Linux Mint and Windows XP. My backlight stays off fine while the lid's closed with XP, but it comes back on randomly with Linux Mint (and most other distros I've tried, actually). So unfortunately I don't get to use Mint as much as I'd like to. I have suspend/sleep/hibernation disabled. I have screensavers disabled. In Power Management, I have "Blank Screen" checked under Actions for when the lid is closed. I have dim disabled and I have display sleep set to "never".
I found a couple threads on Google but no real solutions. I'm hoping somebody here could offer some insight.