White Dots in rendering

I have a model of a kitchen and when I rendered it once, I didn't have any white dots in the rendering. Then I changed some materials in the model, saved a copy and re-rendered with the new materials and I get these white dots. (see image) I tried starting with the original model again and changing the materials again and still I get these white dots. This rendering was done over 24 hours with over 3000 passes using the Test Engine 4 renderer (I like this one better, it gives the lights a more realistic look). Is it just because it's a test engine? Or how can I get rid of those dots? They don't' appear to be linked to any specific material or geometry...