TypeLoadException in Editor after trying to load saved data from disk that just worked in Editor + Build / Play

I'm trying to serialize game data in a binary file and have built several custom classes to hold said data. All my classes are marked as serializable (C#, Windows 7, Visual Studio Express 2013) and everything works very well when I run it in the Unity3d Editor and the first time I Build + Play the game. So far, so good...

Unfortunately, the next time I try and run my game in the Unity3d Editor I get a TypeLoadException error when it tries to load the saved binary file.

I suspect this has something to do with a mismatch between the previous assembly version my data was originally saved out of and a new one created by the Unity3d editor when I run my game in it again (forgive me if I'm way off the mark), but I have no idea how to address this issue if this is the case.

Has anyone run into this before? Am I in the ballpark about what my issue is? Any tips/pointers?

Thanks in advance for lending me use of your gigantic and powerful brain!