This could happen with minor updates (ie. trying to open an SDG file in Strater 5.0 that was saved in version 5.1). If this is the case, File | Online | Check for Update command to update your version of Strater and then try opening the file.
This could also happen with major upgrades (i.e. trying to open an SDG file in Strater 4 that was saved in Strater 5). If you need to upgrade your version of Strater to the current version, you can do so from our online shopping page.
Updated: October 4, 2016