Huh. Looks pretty informative. I'll bet that if you looked at that member variable when the exception occured, it would give you more detail as to specifically what went wrong during serialization since I'm guessing that more than one thing might go wrong.
Erm ... no, it gives you no idea what went wrong beyond a general "serialization error" message. Serialization errors are notorious for being a complete pain to diagnose, to the point where several third party tools exist for that purpose alone.
I've always had mixed feeling about MS help - the contents are usually accurate (and sometimes useful) if you're looking up something specific (like a property, or member), but it's usually pretty useless if you want to find out how to actually do something (like how to serialize a class :-)