Please inspect you database for any orphaned content item records in the sf_content_items table. We have had previous cases where a missing master version of an item might cause this issue. If you find any such records you can remove them through the API.
I hope this helps.
I am also getting this error. How do you check for orphaned content items records? What constitutes an orphan in the sf_content_items table? A sample Sql statement would be much appreciated? How do you remove them through the API?