Can't put 'Description' field in 'Description Zone'

The problem is really very strange!
When i renamed the "description" to another name in the item.xml, E.g. description_item,description1,etc. then it's OK! But if you do this, you also have to modify other files， E.g. item.php(templates/default) etc.

And now, My temporary solution is to insert the values by phpmyadmin.