The following steps will resolve this issue:
1. Download and install SOHO Notes 5.5.2.
2. Launch the OpenBase Manager application (/Applications/OpenBase/).
3. Click the Local button and then select the Chronos_yourusername database in the list.
4. Choose Action > Stop Database and then Action > Delete Database.
5. Launch SOHO Notes. This will create a new database.
6. Choose File > Restore Database > From a File.
7. In the Open dialog window navigate to the following directory on your computer:
~/Library/Application Support/Chronos/Previous Version Backups/
Where '~' denotes your home folder.
8. In the above directory select the most recent backup file and click Open.
This will restore your StickyBrain 3.x database.