I actually found out what happend. After some googling, for nvidia cards, the secondary monitor (if on a different resolution as your first) will stay in 3d mode which uses alot of power which raises your temperature.
I bought a 670 a while ago and I had that same problem, were it stayed in the heightened P stated. I saw that thread but I decided to try a driver reinstall first. I reinstalled the drivers (doing a clean install) and it went away. It came back after a oc induced crash, upon which doing a clean driver install again rectified the issue. I haven't had a problem with it in the last 3 months. However, as I said, it was with a 670, not sure if a 560ti would behave the same way.