I was up in my attic this morning and noticed little bits of ice lying
around---small balls, perhaps 1/4" in diameter. What seems to be
happening is that water is dripping from the roofing nails, then
freezing into the little ice balls. Only some of the nails are wet;
most are dry. I would guess that that makes it more likely that the
moisture is coming from the outside rather than from condensation from
air from inside the house. Is my logic right? Is this normal, or
should I take measures to repair?

Thanks in advance!!
-Ben