I'm sad about that. Thanks for the reply!
You can always downgrade to openmediavault_5.5.19-1, mount/remount your filesystems - they should mount by label, if not restart after downgrade and check again.
Downgrading could be performed as simple as:
Code
cd /tmp
wget http://packages.openmediavault.org/public/pool/main/o/openmediavault/openmediavault_5.5.19-1_all.deb
dpkg -i ./openmediavault_5.5.19-1_all.deb
service openmediavault restart
After you're done you can always upgrade back to current version. It's 3 minutes job.