Hi Anh,
I'm opening this topic up as the linked one below was resolved and you might not have seen the extra replies.
Referred post
Further to the last two posts on above topic I can confirm that data entered in the fields and saved via the backend using the setup in the tutorial for content does save to post_content however the saved content doesn't show in the metabox field when editing.
Changing the code for post_author as in above link doesn't save the data. Do you have any ideas whats going on here?