This is reproducible from mustang b47 onwards on Solaris and Linux.

Attached is an automated testcase to reproduce the issue. The testcase does a dnd from awt list to swt list. It selects an item from the awt list, clicks and drags the item and drops it in the swt list. DnD does not initiate in this case. After selecting the item, if the mouse is moved a bit before starting the drag operation, dnd works properly.

To reproduce:
Run the attached automated testcase