I do have a dual core. In poser, I use 5 threads with no problems. I stopped the render I was doing and set up another with less items in it and set it to 5 threads. I also played around with setting the Lux materials, just to see how it would turn out. It's still rendering after about 2 hours. I know Lux does take longer, though I do wish it were faster. 

So far, I don't think it's having any problems with 5 threads...but then this is the first time using it, so I have no reference as to what, if anything, may or may not happen. :/