Thank you for you reply,
What exactly have you modified in that file? If you don't know how to answer this question, you have probably broken something irreparable in OMV unless you have a backup of the original file.
I obviously did not break anything edtiting config.xml. I just got the same error. So, the suggestion found googling did not work for me. This was the suggestion:
In here, look for <mntent> tags. dev-disk-by-label-NAME maybe listed twice for you (with different UUID's, but the same fsname). Delete any duplicates and any entries that are no longer relevant to your server
But as I said I still get the same error.
As far as the error goes... I just copied it from the error message... using </> does not make it more readable as you can see!