I currently have to, after each time I log in, run
xrandr --addmode VGA-1 1600x1200 and then use the display settings tool to set the correct resolution for one of my monitors.
Also (not sure if this is the same problem or not), during boot up, I don't see the plymouth screen--instead, both of my monitors turn off until lightdm comes up.
I'm using the neauvou driver (or whatever the default is) and Ubuntu 11.10.
So, how can I set the correct resolution for both of my screens from boot?