I am sure you have resolved this by now but for those who have not.... I just ran into this as well. The "fix" seems to be uncheck the "limit disk capacity" check box under each disk in DW Administration. I did find a forum response about "Operation can not be finished because your quota limit has been reached".
Hope that helps somebody else.
Thanks! This is gave me enough information to find what I was looking for.
I am trying to use Workflow Manager to lookup whether a document exists in the file cabinet during a workflow. I would like to create a condition as one document enters the workflow, look into the file cabinet for another document with the same number and route accordingly. Is this possible?