My monitor was flickering after booting Ubuntu 12.10. The problem was increasing if I start moving my mouse and when it is kept idle, the flickering used to stop.
My system has an AMD 32 bit processor with a Nvidia graphics card. In Windows the monitor doesn't have any problem.
In-order to resolve this problem, I had installed Nvidia drivers by following the below steps.
sudo apt-get install linux-source
sudo apt-get install linux-headers-generic
sudo apt-get install nvidia-current
Now the flickering issue is not there. But my system is too slow after logging into Ubuntu. It takes at least one minute even for opening a window. Please let me know how to solve this.