Currently getting errors when running a list approval workflow in a library that requires checkin/out.  The workflow will fail with the following error: "The workflow could not check out the list item. Make sure the item is not already checked out."  "The workflow operation failed because the action requires the document to be checked in."

Because the branches at a number of places, it is difficult to pin point which action is cause the error.

The question is:  Which workflow actions require the item to be checked in?  I have not been successful searching the documentation or this site for the answer.

Any assistance would be greatly appreciated.