I'm experiencing brightness related issues on my MSI GT683 (Intel Core i5-2410M, nVidia GeForce GTX 560M, Ubuntu 12.04 LTS x64, nVidia driver version 295.40). To start with, when I open brightness settings, the slider is working incorrectly - screen is the dimmest on about 1/3 of a bar, moving it to the left side increases brightness. Next, while pressing the keyboard buttons (Fn+up, Fn+down), brightness changes incorrectly - sometimes 2 steps up/down, but sometimes it's totally irregular - ex. in order to set the lowest brightness, I have to set the maximum, then hit Fn+down, then Fn+up. (after 2 moves from 8 to 2... What's even more strange, while changing brightness from keyboard on boot and on login screen, it works perfect. Tried adding acpi related switches to GRUB, but the brightness settings wouldn't work at all. Any help appreciated.