Because there is a lot of confusion on the issue, please could I ask you to confirm that you are explicitly running the program 'as Administrator' (which you have to do each time you run it, unless you change the properties of the executable file, and you stop the the running Eraser process first, to ensure that also starts with administrative privileges), and not just from an account that has administrative privileges.
If you are indeed running as administrator, try a drag and drop erasure when not running as administrator. Drag and drop will not work between windows with different privilege levels; this is an obviously necessary security restriction of Windows.
Please could you also tell us whether the failed task ever appears in the task pane, or whether it remains in the pane after it fails to execute. Context menu and drag and drop tasks should appear in the pane when they are running, and then be deleted if they complete normally.
Also, in the settings pane, enable the Black Box plugin, save the settings and restart Eraser. It would be useful to know whether any kind of report is generated (though this is a long shot as Black Box is really a crash recorder).
There is also a work-around to try. Start a new task, and drag and drop multiple files on to the new task dialog. Those files should be added to the task (this is a 6.1 feature, and it does work in Build 2615 which I am currently using).
David