Move all savegame files out of your savegame folder and try again.
Don't load an autosave file and then save it as normal savegame, you will get similar problems when ioncross loads the files.
I've also found that if Ioncross crashes for some reason, it still can remain a running task in windows and give the same error when trying to launch it again. If so, in task manager if the process FLCharEditor.exe is there, use the "end process" button, then try running IonCross again.