Logged In: YES 
user_id=6405

I'm not sure why this isn't working for you - the "activity"  
property is an interval, and it sorts fine. I've just confirmed that  
the sorting mechanisms are OK (though they were ignoring  
sign *blush* and that's fixed).  
 
Could you confirm that the index page is sorting by the 
"leadtimg" property? Check the url for the sort= parameter.