Ubuntu 12.04.2 with intel i845 graphics becomes sluggish after few minutes of system startup

Ubuntu 12.04.2 with intel i845 graphics becomes sluggish after few minutes
of system startup

I am currently using Ubuntu 12.04.2 LTS installed from LiveCD. It works
fine when system boots but after sometime it hangs for few seconds (about
2 to 4 seconds) showing a garbage screen and then becomes sluggish. It
happens every time I boot my system. I think that it is because of my
graphics card driver. I have intel i845G 64 MB of graphics card. I have
tried updating my xserver-xorg-video-intel graphics driver, but sometimes
it becomes more sluggish at time of boot itself. I am searching for this
solution for a very long time but was not successful. If someone knows
please help me.
Any help will be greatly appreciated.
Saurav Kumar (saur.k10@gmail.com)