Thanks Wolfsoul, I don't have that option, just options to adjust the screen position. Interestingly, the problem also manifests itself when I lower the desktop resolution as well.
I don't thin we've missed the option, as frankly there aren't exactly a million options in the display panel. I can only assume it has something to do with the driver. As you said Devandal its odd that it worked before, and since the upgrade it has stopped.