If you try to save a content profile again, after saving it a first time, you get the error: "This content has been modified by another user, changes cannot be saved.".
This seems to be caused by the fact that the form is redirected to itself after saving, but drupal doesn't update the field "changed" inside the form rendered to the user, so it stays set to its value from the first time the form was rendered, which is previous to the fresh made save. It seems to be related to http://drupal.org/node/394694.
Steps to reproduce this bug:
- install content_profile module
- create a new field like "Full name" inside content type "Profile"
- select "Show a tab at the user's page" on page "Content types > Profile > Content profile"
- go to "My account > Profile"
- write something inside "Full name" field
- click on "Save" button => the profile node gets created and the form is displayed again
- click on "Save" button again => you get the error mentioned above