Hi Paul, yes, I dont normally use it except when doing a dve site so I dont confuse dev backend with the live and muck up live site. (been there done that) - you can change it back if you want.
The olderversion, which is working on the other site is 1.7.2 (downloaded 25/05) - the current (new) version is also 1.7.2 but downloaded yesterday.
I am thinking conflict might be elsewhere (another zen plugin/template update) as works fine on other 2 sites.