Macbook Pro Retina - nVidia card does not work correctly

Hi,

having a MacBook Pro Retina. It ran fine till yeasterday when I fired up a game which was laggy and it was running fine before. It took me several hours to find where the problem is and it seems to me that the nVidia dicrete card is not working. But strangely not working. I installed gfxCardStatus to see whether the card is being switched to run the game and it actually is. But the performance is the same as running it on an internal Intel. I took another test and downloaded CINEBENCH to see the differences and sadly the results are the same if I switch to nVidia or to Intel and run the benchmark.

Obviously something is not right here. It happened over night. Before it worked corectly. I do not remember installing something that day/night that could have broken it (in case it is a SW problem). Only one thing comes to my mind - Apple Java update. But I tried to uninstall it and got the same result. I did try to restart several times. But otherwise there is no visible flaw, e.g. flickering or black screen when swithech do nVidia - nothing. gfxCardStatus shows that the system switches the card and I notice no change. Only in heavy load it is obvious that it is slow (slower than it was).

Is there a way to see if the nVidia card is working? I suspect that even if the system is trying to switch to a discreet card it still runs on the Intel in reality. Any way how to distinguish this rather than to rely on gfxCardStatus? Any log that would make this clear? Any test I can run (Apple HW test shows "no problem detected")?

Many thanks for hints.