problem mapping from protege in jess

hello all
my frustrating problem is that i can't get started with anythig,because i can't map a class a class already created in protege...in jesstab ( i use protege 3.4 with jess 7.21) i receive a message like :
  Jess reported an error in routine mapclass
       while executing (mapclass Person).  
          Message: Protege class not found: Person. But the class is there,created already... strange enough,in the lab of my faculty it naturally works just fine :)...I even tried to create a test class with jesstab,then mapclass it, and it worked...but when i tried to access a slot,it would find it ! For instance :

Jess> (deftemplate person(slot name)(slot age))
TRUE
Jess> (defclass P(is-a :THING)(slot name(type string))(slot age(type integer)))
TRUE
Jess> (make-instance of P(name "John")(age 30))
Jess reported an error in routine make-instance
        while executing (make-instance of P (name "John") (age 30)).
  Message: Protege slot not found: name.
  Program text: ( make-instance of P ( name "John" ) ( age 30 ) )  at line 3.
Jess> (reset)
TRUE
Jess> (make-instance of P(name "John")(age 30))
Jess reported an error in routine make-instance
        while executing (make-instance of P (name "John") (age 30)).
  Message: Protege slot not found: name.
  Program text: ( make-instance of P ( name "John" ) ( age 30 ) )  at line 5.
Jess> (mapclass P)
P
Jess> (make-instance of P(name "John")(age 30))
Jess reported an error in routine make-instance
        while executing (make-instance of P (name "John") (age 30)).
  Message: Protege slot not found: name.
  Program text: ( make-instance of P ( name "John" ) ( age 30 ) )  at line 7.


What kind of error do i make?
Thx