You have added these lines to your mt.cfg file, correct?
DataSource ./db
ObjectDriver DBI::mysql
Database cpanelname_dbname
DBUser cpanelname_user
And uncommented the following lines in the mt.cfg file, correct?
DBUmask 0022
HTMLUmask 0022
UploadUmask 0022
DirUmask 0022
And added your password to the mt-db-pass.cgi file
That's all I can think of.