See "Joe's" comment here: http://drupal.org/node/139915
Go to [Content management] > [Content types] > [Manage fields] and make sure yiour image field is LIGHTER than [body] eg -2
this will force the image above your teaser but not yet inline
then go to modules > system > defaults.css
and add
.field-type-image img {
float: right;
margin-left: 1em;
border: 0px solid red;
}
Note: my CCK image field is called "image" and I choose to float it right, adjust yours to suit your tastes.