Symptoms

 This error keeps surfacing: "Server Error: Could not load file or assembly 'Control' or one of its dependencies. The system cannot find the file specified."

Community Control:
-DragAndDropFile:Input=DragAndDropControl.DragAndDropFile.Control, Control 
 

Diagnoses

Perhaps you are experiencing an issue with the DragAndDropFile control's "FullName" as per: 
 

Resolution 

http://community.k2.com/t5/K2-blackpearl/Drag-and-Drop-Upload-Control/ba-p/63942

Please know that K2 community projects/custom projects are usually not supported by K2 Support and the owner of the controlcomponent should be contacted should you run into any issues.