Kashrut

“May I add dairy ingredients to bread that I intend to serve with a milchig meal on Shavuos?” “Is one permitted to eat the local bread when everyone knows it is milchig?”

How can two kosher, pareve ingredients combine to become a product that can become non-kosher? A non-Jewish friend of mine makes her own raisin wine. Is this a kashrus issue like grape wine, or is it like cherry wine, which is usually kosher?