Dahon D7HG Handlepost hinge loosens pivot point
Please review the following two references as it possibly your D7 may be fall within the questionable Dahon models:

http://www.performancebike.com/images/performance/web/pdfs/Dahon_Folding_recall2009.pdf

and

http://www.thorusa.com/dahon/technical/recall.pdf

(Dahon enthusiasts have a blog as well that may be accessed through the manufacturer's website and is useful for service tips as well.)