Hi Lara, version 4 is not released yet it is still in beta release. The beta versions expire after 6 months or so, so yes during the beta period you need to download the current version when an old version expires.

The cost to upgrade from v3 to v4 will be $100 but if you ordered v3 within the last year you will be able to get a free upgrade.

I'm not familiar with the error message you show there. Do you mean that v3 was installed and working on your computer but now when you try to run it you get that message? Or are you getting that when trying to install it now?

If it is during installation it could be a partial download, try deleting it and downloading it again from http://moi3d.com/reinstall.htm .

- Michael