Can't change display resolution on Ubuntu 12.04

view story

http://askubuntu.com – I'm using Ubuntu 12.04 on my Lenovo G575 (64 bit). I was using my computer with the 1366x768 display resolution. I changed the display resolution of my computer to the 800x600 yesterday, then I tried to return it back to 1366x768, but I couldn't. When I try to change resolution, it's getting dark and it crashes. Then nothing happens. So I need to restart to open my computer. I used many methods which is written on the net to return the resolution back, but all these methods didn't work :( NOTE: When I create new user, the resolution for new user automatically is setting to 1366x768 and I ca (HowTos)