Locate the file user.config in the following directory. Note that some folders in the path may be hidden by default under explorer:
C:\Users\[your username]\AppData\Local\ReefMaster_Software\ReefMaster.exe_Url_xxx\2.1.52.0\user.config
Delete this file, if it exists, and try to start ReefMaster again. Please let me know if the problem persists.