No. I don't recall specifically the cause of the nostril glow, but it is not specific to poser (not a bug) and it is not caused by the lights seeping through the head. Nostril glow's been around a while -- the orginal no glow nostril props are found at www.morphworld30.com for older figures. If I recall, it has something to do with the way the things are set up, but I really don't remember (been way too long). Another option in P4 is to apply a solid back reflection map to the nostrils. Sounds odd, I know, but I've used it a few times with good success. Been lots of good pictures that make fun of this effect, and everyone gets it sooner or later.

thou and I, my friend, can, in the most flunkey world, make, each of us, one non-flunkey, one hero, if we like: that will be two heroes to begin with. (Carlyle)