If you use the OOTB approval work in sharepoint 2007 to update approval status on the library/list that requires "content approval". And you also check the option to "Start this workflow when an item is changed.". Your work flow will go into an indefinite loop.This is know bug in SharePoint 2007 built in workflow.
When the workflow update the approval status of the item/document, system considers that as a "change", trigger a new instance of the workflow. Again and again.
So if you would like to use the built in approval workflow to update approval status, don't use the option to "Start this workflow when an item is changed.". If the content ever gets modified again the approver would not know through the workflow.The contributer either has to remove the old item and update it as new, or, set up alerts for approvers to get notified all the chagnes and approve the content outside of a workflow.