Unrendered Pixels WIth Iray

I am rendering an Animation and there are some pixels that are not getting rendered for some reason. I'm attaching an image containing two sequencial frames. You will see a few white pixels in each image. Does anyone know what is causing this?
Update - The pixels appear to be transparent since they show up black in some apps and white in others. I tried some things that I found refarding Fireflys. I reduced the lighting from my light source. I made sure that the Firefly setting was ON in Rendering. I checked the Reflectivity settings for her skin and they are all under the 70% threshold.
It also appears that if I Render the image as a Single Image, it seems to look fine. I would need to do some more thorough testing to verify this.


Comments
This can happen if the SSS Scattering mode is set to Chromatic, depending on other settings, so it may be worth trying to set it (in the Surfaces pane) to monochrome.
It does seem to have gone away after changing SSS Mode to Monochrome
I take that back. I must have fixed the previous ones with a different change that I made. I am still getting it with SSSMode = Mono a little further into the animation.