The reason why the 2nd query "does not work" is Open World Assumption, and possibly also (the lack of) Unique Name Assumption.
Say you state:
John lives in Paris.
Mary lives in Paris.
The following questions are answered in the following way by an OWL reasoner.
Who lives in Paris? John, Mary
Does at least one thing live in Paris? YES
Do at least two things live in Paris? Maybe
Is Paris a person? Maybe
Is John and Mary the same thing? Maybe
Is Paris and Mary the same thing? Maybe
Does at most one thing live in Paris? Maybe
Whenever the OWL reasoner comes back with a Maybe, the user interface (such as Protege) tends to show nothing.
In order to get the answers that you probably want, you need to add a lot more information to the knowledge base, e.g.
Mary is not John.
Everybody who lives in Paris is either John or Mary.
Hope this helps. Looking at how few views your recent questions have received on Stack Overflow, I'd say it's better to ask these questions on the Protege mailing list for the time being. Or even better, look at the mailing list archives. The Open World Assumption related questions come up at least once a week there.