Manager Serialisation Exception

I can not open Manager on my MacBook Pro it keeps coming up with a message Manager.SerializationException What does this mean and what can I do???

Try to upgrade to the latest version.

For now updating has worked but I have had to do this on a few occasions and also for other reasons. How many times do you have to update to keep Manager operating. I always fear I will lose my data entries.
What is the best way to save?
Can I copy from Mac to Windows?

This error happens when you run newer version, then revert back to old version (old version doesn’t understand new version data format).

Yes, you can copy data from Mac to Windows.

Thank you for replying and so prompt. Can you tell me how to copy from Mac book to my windows.