new install of 1.8.8 - DatabaseException:ScriptNotFound

aloha!
i am in process of creating a fresh install of 1.8.8 on a server that already hosts successfully an install of 1.7.
i get as far as the database setup page in the install process and see :DatabaseException:ScriptNotFound

i haven't yet found why this is.. i have created an empty database and pointed settings.php to it and given correct details in there.

any ideas?
thanks