Prime95 stresses the CPU. Furmark and games primarily stress the videocard. You have a GTX 560 Ti, which is rated at 170W-210W depending on which version you have. The CPU is rated at 125W in comparison. I did a Google search on "2509 LPM 16-25" and didn't get any results that said "this is a quality power supply".
This all adds up to me thinking that as your videocard draws more and more power, it becomes too much for that power supply to handle and your system becomes unstable.
Thanks, i replaced the PSU and its work now!