Hi Sean,
Tried that but no luck.
The problem was the Yahoo hosting - when you create a db in their 'control panel' the db user created has limited permissions - doesn't allow table creation (!) & I couldn't see a way of resetting or changing those permissions. I am pretty new to all this though. So I installed phpmyadmin, created a new database and it worked - the user has full permissions. And the "@localhost", well it seems to add "@localhost" to the username created, even though the server is mysql - in the database that works, the db user is still 'riverq@localhost'.
The CMS works up to a point - very slow indeed and throws up a load of code inside the main CMS window each time. You can still update the site, although it gives a javascript parse error on publishing. And the blog module doesn't work at all. So advice for Yahoo hosting and SS 2.4.2 is don't bother!
Thanks heaps for all your help though,
Cheers