Carrie W. is completely right, as the same exact thing happened to me and was devestating. My milk, once frozen even for ONE OR TWO DAYS started producing an enzyme called lipase, which eats away the fat in the milk and causes it to taste a little soapy rather than fatty and sweet, as BM typically tastes. I'm pretty sure it's still safe to drink but it may not be as nutritious and certainly not as tasty. My son drank the milk like this for a few weeks but then started to turn away and reject the bottle. We couldn't figure out what happened, until we started defrosting all of my frozen milk, experimenting with it and found that ALL of my milk had this yucky taste. I researched it extensively, talked to two lactation consultants, and my pedi and there was nothing I could do. I learned that I could hold the milk in the fridge for up to a week and then toss it but there was no use in freezing it for me, as it would pretty much go bad. I say this was devestating because I pumped like mad, hoping my son would be able to exist on my BM for six months after I stopped nursing. I pumped so much that I filled up 1.5 of my own freezers (we bought one just for my milk), my sister in law's freezer, and two of my friend's freezers, and all that milk went to the garbage. It's completely awful but at least you now know and may have to pump less. I'm sorry - it sucks big time either way.