I agree with lineaway, I have seen and fixed more than one buddies brakes because of contaminated pads over the years and most often its an oil based product, including but not limited to WD40, that got on the pads. Comments are always something like, but its just a little over spray (of what ever the product was), and no matter how much cleaning, heating, or other attempts I have tried to get it working again in the end only proper cleaning of the disk, new pads, and a good heat cycle and water quench has been the fix.
My exp and 2 cents for what its worth.