Hi Romeo,
Does the editor apply the styles to the finished page, or is it just what you are seeing in the editor area?
If you type in some text to the editor area, and click the 'source' button, does the source show the unwanted formatting?
In iRite (I think) you can specify the initial styles of the editor area in the: fckeditor/editor/css/fck_editorarea.css file (near lines 30-45).
The values entered here should reflect your site's body styles.