Somehow your ScreenshotCaptor.ini file got messed up -- quite possibly a bug in an older beta that kicked in when you ran the new installed and it killed the running instance of the older beta.
I've uploaded a new version of 4.0 that has an additional protection against the possibility of corruption occurring if it crashes while saving settings; if you downloaded 4.0 earlier than 2:30pm central (forum) time, you might want to re-download.