Cannot overide registration form's cck fields

Hi,

I'm theming my user registration form via a preprocess function yet although I can override the field group's title I cannot override any of the CCK fields. Their original values as created in the content type always display on the user registration form.

$vars['form']['group_cprofile_personal_info']['#title'] = t('Your Personal Information'); <-- works
$vars['form']['group_cprofile_personal_info']['field_cprofile_postcode']['#title'] = t('Postcode where you live'); <--doesn't work

I'm using 6.x-1.x-dev version of Content Profile with Drupal 6.17. Does Content Profile have any know bugs regarding the above?

Thank you.