Quick update : I noticed just a few days ago that my ppd was down more than it should be... I checked the stats in GPU tracker and the GPU that is hooked up to my screen has been failing pretty much every single 803x WU after a just a few % (3-5) !!!
So I reset the overclock on it but nothing changed, it was still failing miserably. Interestingly, I have the exact same video card folding happily, and overclocked, in the same machine. The driver I was using was 260.99.
I pocked around the web, and it seems that this is a known issue that is fixed by the 301.24 nvidia beta driver. Sure enough, since I installed those drivers (yesterday), all WUs have completed successfully !
It's not perfect, sometimes IE lags a little. I have to look around a bit more to see if this can be fixed.
I any of you has issues with drivers and/or the latest WUs I suggest you try the 301.24 drivers.
Hope that helps !