I believe everyone is missing the boat on this one. The key bit of information is "and then frozen." The same thing happens to me when I make ice cubes (from our Pur water filter) and then drop them into a glass of water. When the ice cubes melt, they leave behind "floaties" in the water. Marilyn von Savant answered this question several years ago in her Parade Magazine (a Sunday paper national suppliment) column. If I remember correctly, freezing the water does something with some of the minerals present in all water (except distilled) that causes them to become visible and float around. So don't sweat it, there's nothing wrong with your cleaning regime.
