We send any vials that have crystalizing over to sterile processing and in a very short time they return them good as new. We keep all of our vials in a hot box with the light bulb like others have said and that usually is all it takes. We don't have very many that ever need any attention.
I appreciate all of your input on the many ways to de-crystalize my mannitol. I finially went to the farm supply store as Colleen suggested and got an egg incubator, thank you Colleen. It works great!!!