the DPMS option in the device section shouldn't be there, it should be in the monitor section.
Try to insert this line in modules section:
and copy this at the end of the conf file:
those options were there by default...
the only weird entries i see are:
Mar 12 15:52:12 localhost kdm: Server for display :0 terminated unexpectedly
Mar 12 15:52:14 localhost kdm: Server for display :0 terminated unexpectedly
Mar 12 15:52:14 localhost kdm: Display :0 is being disabled (restarting too fast)
but you can read it yourself here
if you want
apparently "nvidia" isn't loaded