Smw_import_ is broken which prevents quite a few use cases for SMW to take place, including collaborative vocabulary creation and full-featured RDF export.
More info is available in this thread:
Markus, please update this with more details about the culprits - I'm not sure about what needs to be done:
There have indeed been some changes there somewhere around SMW 1.3/1.4. I assumed that this is a very rarely used feature, hence did not send any warnings. Effectively, there is currently no more datatype enforcement for imported properties and you always need to specify the property datatype explicitly.