XMLSerializer, part 2

After spending more time fixing bugs and digging into XMLSerializer (see my previous post), I've come the the following conclusions:

1. I'm still satisfied with my design where I split the "data" into a separate class. It makes it much easier to quickly see what is being serialized and what is not. If I hadn't done this, I would have reorganized the fields in my objects to put all the serializable fields together, so I could put all the unserializable fields (with their corresponding noisy attribute tags) in a separate section of the class definition.
2. I figured out my problem (mentioned in bullet item 3 in the previous post). I had not provided a default value for an enum in the class definition. Once I did that, the uninformative error message went away and my object was sitting happily on disk.

On to the next learning experience...