I have been having issues with my graphics driver so I figured the first step ought to be to update to the latest stable release.
Initially I tried updating via the Ubuntu repositories but the updated driver they had did not agree with my system at all and after a bit of effort I was able to get back to the original driver which at least gives me a functional system most of the time.
I have an ASUS M3N78-VM mainboard (http://www.asus.com/Motherboards/M3N78VM/) with onboard graphics consisting of the GeForce 8200 chipset. The OS is Ubuntu 64-bit 14.04.
My understanding is that this is referred to as the GeForce 8 series on the site here and that therefore the correct latest driver for that would be the Linux 64-bit 340.76 driver released on 2015-01-27.
If someone can confirm I am barking up the right tree I would apreciate it.