So some super wierdness ... I've re-encoded the offending movie from the BD with a newer version of HB and it still doesn't play !!!
I run everything through MetaX on the PC so will now try that out, although it will be mighty strange if that's the issue as it doesn't seem to effect anything else I've done recently ...
does the file have chapter tracks? If it does not have any, MetaX on windows will create a hidden chapter track that seems to throw off the file on iOS7. Even if you delete the default chapter track on MetaX it will still embed a track, this seems to be a glitch in the last few releases of MetaX