When we release big updates, sometimes your save files can be incompatible. You may want to continue playing an older version of the game so you can keep playing your saves without problems.
You might also want to check out an older version and see how the game has progressed. Feel free to expolore!
Open InfraSpace Properties
Select the Version you want
"None" means no special version, i.e. the newest available version
Other platforms work similarly if they support version switching (GOG does).
Can't load your save even though you should be able to?
Send it to us and we'll fix it for you: support@dionicsoftware.com