I found that my nvidia configuration settings were not being loaded at start-up,
Try - System>Preferences>Startup applications, select 'add' and name it something like 'nvidiastartup' and in the command line (the important bit) insert this text "nvidia-settings --load-config-only" (excluding inverted comma's) then click 'add', now your nvidia configuration will run at startup.
just an update on my last post,
I found that my nvidia configuration settings were not being loaded at start-up,
Try - System> Preferences> Startup applications, select 'add' and name it something like 'nvidiastartup' and in the command line (the important bit) insert this text "nvidia-settings --load-config-only" (excluding inverted comma's) then click 'add', now your nvidia configuration will run at startup.