Sudden rMBP graphic performance issues

Hello,

I've a MacBook Pro with Retina display, running 10.8.2 and Win7 64-bit (via Bootcamp).

It's since a couple of days now, that I'm noticing a sharp drop in my rMBP's graphic performance. This is best observed in games, running both on OSX and Windows. For example, I've played a lot of Diablo 3 with this computer, under OSX, on standard resolution (not retina), and it played very well, and really smooth. When I ran it today, it lags really bad (i.e., running at very low FPS). It's unplayable. This shift occured overnight. One time it worked, then suddenly it doesn't.

I've observed this playing Borderlands 2, under Windows (Bootcamp). This game used to run just fine until this 'performance drop' occured.

Did some testing;

According to System Information, when I'm just browsing the internet, my machine is using the Intel HD 4000, and when I run Diablo 3, it then switches to the Geforce GT 650M. I get very poor performance. Then, while the game is running, I ran Activity Monitor only to see my system totally chilling. Had 93% CPU Idle, 10.5GB free RAM, hardly any disk activity @ peaks of 1MB/sec. I then ran atMonitor, which apparently monitors GPU load and temp. the GPU was at 99%, and I'm not sure about the temp. I assume it went up as well.

I'm not sure what exactly caused this shift. Is any familiar with this? Any bright ideas?

Thanks. All the best,

-w00fa