Comment #2 on issue 941 by acampb...@ltufz.com: Get Library Instance instantiating 2nd library instance
http://code.google.com/p/robotframework/issues/detail?id=941
On further inspection, this was a library scoping issue. Adding ROBOT_LIBRARY_SCOPE = 'GLOBAL' fixed it.
I was importing this by the keyword Import Library, as a module, and in RF User Guide it states that libraries imported by module are global by default. So I would recommend closing this ticket as resolved (or unreproducible) but I think that either the Import Library keyword should be documented as to this behavior, or modified to import as 'global'.