As is mentioned in the installation guide, this has to do with the way Ozone works. The problem comes about when, after some data have been "persisted" to the file system, a newer version of OpenEFM is installed. The Ozone data are really only compatible with the version of OpenEFM that created them, and the newer version is unable to read the existing data.
To fix this, you unfortunately must wipe out all your data, which by default are stored in "/var/OpenEFM/data/". Deleting the contents of that directory should eliminate the exception.
Update Author: Jason Van Cleve
Original Author: Jason Van Cleve