From innuOS 2.0, we have started using exFAT as the filesystem for our backups due to the wider compatibility between Windows and Mac OS X. However, Mac OS X requires some specific conditions to be met on the way the partitions are created. We are adapting this on version 2.0.7. Once this is done, you will need to recreate your backup disc.
Version 2.0.7 is now available and should resolve this issue. Please contact Support if it's not the case.