Follow-up
I have since done a complete reinstall of Vista x64 ultimate and MCE functioned perfectly...
UNTIL, I went into recorder locations. MCE hung for a while, then showed the storage location on 'C' - which was not editable, and since then has shown the exact same symptoms as my post above.
I'm just hoping someone will notice this and offer some ideas? Is it to do with the WHS setup affecting the storage locations in MCE? I only really went into the TV recorder locations to direct the local storage to my 'D' (data) drive rather than the main system drive.