I had a similar problem in the past and they only showed up when I rendered in different settings.  My solution was to adjust the lighting a little by moving the light position, and it went away.  To this day I have no idea what was going on.

My guess is that the file I was using some how became corrupt and caused the problem.  I'm saying that because I think I opened a new window and used a new load of the model and the texture and the problem didn't occur with the new load of the model.