Hi did you ever figure this out? I just did after having the same problem.
I had renamed all the wp tables in the database and updated the config.php. The blog continued to work normally until I tried to log in and kept getting:
You do not have sufficient permissions to access this page.
I have found out that just renaming the tables and updating the config wasn’t enough. You have to update three records:
go into your phpmyadmin to your _options table find record: wp_user_roles or xxx_user_roles and rename it to match your table prefix.
Next go into your wp_usermeta or xxx_usermeta table find and edit: wp_capabilities, wp_autosave_draft_ids and wp_user_level
and do the same thing, rename to match your table prefixes.
Things should begin working for you after.
