I would actually suggest submitting a case to Tech Support on this one. Support Case | Tableau Software
I can't be sure, but I've looked around at our internal records and this error seems to usually indicate either a corrupted workbook file or be a manifestation of a product bug.
We just encountered this error ourselves. It looks like a known issue that has been fixed (in case you haven't upgraded):
Thanks for the updates. Looks like the issue has gone away. I'm guess it was address with on of the upgrades. Thanks for the feedback!!