How do you mean it doesn't fit right at certain parts? Can you please post a picture in your 3d thread?
As for losing previous unwrap work, make sure you always collapse the UVW Unwrap modifier onto your model after doing UV work. All UV modifications gets saved that way and when you apply the UVW Unwrap again it remembers what you've done earlier.
Another thing, although unlikely, but there's a chance you have been working with different UV channels within UVW Unwrap. There's a setting in there that allows you to save multiple UV sets on the same model. Make sure that's always set to the same on you worked on before. It shouldn't change on its own but, you know, it's 3ds Max so it's got a lot of bugs.