iI also get the same problem and resolved with following url...please check:
https://niravchauhan.wordpress.com/2013/08/12/wrong-content-type-dhl-internetional-potencial-bug/Goto app > code > core > Mage > Usa > etc > Config.xml
Add Below code at <carriers> <dhlint>
:
<content_type>D</content_type>