Just a quick update on this, it may provide a clue to my issues. I was booted off the server where I have xerte hosted twice today for mod_security violations, specifically rule 340016 which Google tells me "This occurs when using the code editor to edit php code. If you try and save code changes (by pressing the edit button at the bottom of the code editor) and you do not receive a confirmation pop-up message, then this is the most likely cause."
What triggered it was just a bit of trial and error to try and figure out what was causing the problem. I was copying text from one of the V2 LO to a new V3,1 LO. When I came to something preventing it publish I would keep stripping it back to try identify the problem. I had stripped it back to a couple lines of plain text and that was still throwing up the error which led to my IP being blocked?