Basara, thanks for reply but unfortunately its not as simple as that. I only had 1 login (the original admin). I added a new User Group, which only had "Access" but no "Modify", I then managed to change my Admin onto this user group leaving me with no user at all as a Top Administrator. Because I could not change certain things I decided to change the username also.
I can logon with the new username but can only "Access" and not "Modify" and when I try to logon with my admin username and password it tells me there is No Such User.
This has to be a BUG where you can lose the ONLY Top Administrator!!