Thanks for those links Ingo, It sounds like they're going in the right direction IMO.
Let me know if you want a copy of the CMS database I'm having an issue with, I'll be re-installing later today. I am using symlinks for the sapphire , cms and jsparty directories on that install but have not been able to reproduce the issue elsewhere with the same config so that's what leaves me with the thought it's something in the database.
It was completely my fault because I misunderstood a setting in _config.php or in my case _ss_environment.php and this behaviour is by design. explained here: http://doc.silverstripe.com/doku.php?id=recovering_password