Why am I getting the error "Coercion Failed: Input cannot be null for this coercion"?

Question

I created a OOTB team site, with a OOTB document library and an OOTB "Approval - SharePoint 2010" workflow.  Under the workflow's start options I have "Allow this workflow to be manually..." checked.  On the next workflow setup page, I put
myself in the Assign To field and put "test" in the Request field.  I left everything else blank. 
Then, I setup a retention stage in the Information Management Policy settings for the library.  The event is Modified + 1 days, action is Start a workflow and I selected the workflow described above.  I set the Recurrence for 1 days.
If I execute the workflow manually, it executes without error. 
When the IMP executes the workflow, the status indicated in the column added to the library is "Canceled".  Clicking on the Canceled link opens the Workflow Information.  In the Workflow History section the Event Type is Error, User ID is System
Account and Description is "Coercion Failed: Input cannot be null for this coercion". 
Research shows that this error can be invoked when creating custom workflows that contain empty input fields when executed.  I would think that if there were required input fields in the workflow
configuration, that the workflow would error when manually executed. 
Any help is appreciated.  Thank you.
Matt H.

Answer 1

I had found that article previously but it doesn't seem to apply since this is OOTB and not a workflow created in SD.  I would expect that MS would have created the workflow in such a manner that it would work with IMP.  Besides, I don't think
it's possible to edit the default Approvers workflow.  Also, I'm sure I'm not the first one out there to use the Approvers workflow with IMP.  If it was broken OOTB, someone else would have discovered it.  My guess is that there is something
not configured correctly on the server, but I don't know how to start to diagnose it based on this error message.Matt H.