nvidia - Ubuntu 14.04 Running Low Graphics Mode After Upgrading Software

I'm having problem with my PC. It says "System is running in low graphics mode"
I'm using nvidia gt430 graphics card. Everything was ok after installing Ubuntu 14.04 but after installing software updates the error happen, i can no longer use my pc, The last thing i remember the default graphics driver I used was xorg nouvou driver.
Please help me I already reinstalled ubuntu 3times but have the same problem. I don't know what to do.