Root object person.getPerson seems to not work properly

[ghost]

Hello everybody!

I'm writing to get some help or some idea about why something is happening in my Alfresco Content Service environment. I have built some extensions over my instance using Javascript based Webscripts. All of them work perfectly, however I do have one exception. The problem is: in one webscript I invoke the Javascript root object person.getPerson in this way:

 var userNodes = people.getPeople(null,0);

And it doesn't return anything, however, I do have some users registered in my instance. Also, I can see all of them using the node browser and the following Alfresco-CMIS query:

 SELECT * FROM cm:person

I tried to test the same webscript in a test instance and it worked without problems. So, I don't think the code is the problem. In addition, I have read the implementation of the root object. And I discover that, "under the hoods", the code creates the following FTS query and passes it to the SearchService:
TYPE:"{http://www.alfresco.org/model/content/1.0}person" AND ("***")

I tried to verify this query in the node browser too and it didn't return anything too. I also tried to remove the "AND ("***")" snippet from the query and then it worked without any problems.
Do someone knows what could be and why the query without "AND ("***")" works properly?

Some informations about my environment:
Alfresco's version: 6.2
Edition: Community

Thanks in advance!
Felipe