Long delay when using JComboBox.setSelectedIndex() ??

Hello,

I am attempting to load 5000 employee items into a jcombobox, and then setS=
electedIndex, but I am getting a odd delay in the gui after setting the sel=
ectedIndex

1) If I load the 5000 employee names using a simple vector, it works fine. =
When I call setSelectedIndex(5), it sets the combobox to the 5th element, v=
ery quickly. This works fine:

 while ((line = input.readLine()) != null) {
                StringTokenizer st = new StringTokenizer(line, "|");
                lastName = st.nextToken().trim();
                firstName = st.nextToken().trim();
                id = Integer.parseInt(st.nextToken().trim());
                 comboBoxItems.add(lastName);}
                
                mybox1.setModel(new javax.swing.DefaultComboBoxModel(model)=
);
                mybox1.setSelectedIndex(5);

2)HOWEVER, if I load an employee object into a mapped vector, and then setS=
electedIndex(5), I DO see it instantly set the GUI combobox to the 5th item=
, BUT then there is a LOOOONG delay in the gui (1 minute or more) before it=
 allows me to do anything further in the gui

 while ((line = input.readLine()) != null) {
                StringTokenizer st = new StringTokenizer(line, "|");
                lastName = st.nextToken().trim();
                firstName = st.nextToken().trim();
                id = Integer.parseInt(st.nextToken().trim());
                empBuffer= new Employee(id, lastName );
                map.put(empBuffer.getId()+"",empBuffer );
                count++; }
                
             model.addAll(map.values());
             Collections.sort(model);
             mybox1.setModel(new javax.swing.DefaultComboBoxModel(model));
             mybox1.setSelectedIndex(5);

public class Employee implements Comparable {
         private int id;
         private String name;

         public Employee(int id, String name) {
             this.id = id;
             this.name = name;
         }

         public String getName() {
             return name;
         }

         public int getId() {
             return id;
         }

         public int compareTo(Object emp) {
             return getName().compareTo(((Employee)emp).getName());
         }

         public String toString() {
             return getName()+","+getId();
         }
     }