> I can just delete the appropriate rows, but I'd rather use the user
> manager
> interface.

I tried this in phpMyAdmin and I looked in the MySQL docs, it appears that
you need to modify the table directly. phpMyAdmin does the following:

# Deleting 'fred'@'%' ...
DELETE FROM `user` WHERE `User` = "fred" AND `Host` = "%";
DELETE FROM `db` WHERE `User` = "fred" AND `Host` = "%";
DELETE FROM `tables_priv` WHERE `User` = "fred" AND `Host` = "%";
DELETE FROM `columns_priv` WHERE `User` = "fred" AND `Host` = "%";

# Reloading the privileges ...
FLUSH PRIVILEGES ;

If you find another way, please post to this thread. :)

Joe