I took a look at your screenshot of your control panel. The Coolbits utility should have a "find optimal settings". Can you find it? If so, try to see what settings the system gives. Test those in CSS.
When Oc'ing manually raise the clock speed in 5 Mhz increments until the card no longer passes the test, then take it back down by 5Mhz.
Try a game offline and have the Nvidia control panel running in the background (or have a similar monitoring utility running). Once you have stressed your card, flip to the Desktop and check your temps to make sure that they are not too high.
You could also try ATI Tool for Nvidia or Rivatuner. I have little experience with those utilitlities, so wait for another member that is qualified ro comment on those.
Hope this helps.
P.S. I visited Greece a couple of years ago - Awesome!
I took a trip out to the Ionian Islands (Kephalonia and Ithica). The trip was supposed last 4 days or so, I ended up staying almost 2 weeks, it was so beautiful
. I wanted to stay longer, but was running out of money. It was really nice to follow in the footsteps of Odyseus on Ithica. I hope to return.