FULL PRODUCT VERSION :
java version "1.6.0"
Java(TM) SE Runtime Environment (build 1.6.0-b105)
Java HotSpot(TM) Client VM (build 1.6.0-b105, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [Version 5.1.2600]
Microsoft Windows 2000 [Version 5.00.2195]


A DESCRIPTION OF THE PROBLEM :
In an editable combo box inside a JTable, when using the keyboard, presing enter or the space bar doesn't select the highlighted item. This worked with JDK 1.5.0.08.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Select the editable combo box
click esc to open the drop down list
using the arrow keys highlith one of the items
press enter (or space)

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The highlighted item should be selected
ACTUAL -
with enter the list is closed and nothing is selected, with the spacebar nothing happens.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import javax.swing.DefaultCellEditor;
import javax.swing.table.TableColumn;
import javax.swing.table.TableColumnModel;
/*
 * Test.java
 *
 * Created on May 3, 2007, 1:29 PM
 */

/**
 *
 * @author  helm-youngs
 */
public class Test extends javax.swing.JFrame {
    
    /** Creates new form Test */
    public Test() {
        initComponents();
        getContentPane().add(scrollPane);
        pack();
    }
    
    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    private void initComponents() {//GEN-BEGIN:initComponents
        editableComboBox = new javax.swing.JComboBox();
        scrollPane = new javax.swing.JScrollPane();
        testTable = new javax.swing.JTable();
        
        editableComboBox.setEditable(true);
        editableComboBox.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Item 1", "Item 2", "Item 3", "Item 4" }));
        
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("Test");
        testTable.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null}
        },
            new String [] {
            "Title 1", "Title 2", "Title 3", "Title 4"
        }
        ));
        TableColumnModel columnModel = testTable.getColumnModel();
        TableColumn tableColumn = columnModel.getColumn(0);
        tableColumn.setCellEditor(new DefaultCellEditor(editableComboBox));
        scrollPane.setViewportView(testTable);        
    }//GEN-END:initComponents
    
    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Test().setVisible(true);
            }
        });
    }
    
// Variables declaration - do not modify//GEN-BEGIN:variables
    private javax.swing.JComboBox editableComboBox;
    private javax.swing.JScrollPane scrollPane;
    private javax.swing.JTable testTable;
// End of variables declaration//GEN-END:variables
    
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
using alt+up or down arrow selects the highlited item.

Release Regression From : 5.0u11
The above release value was the last known release where this 
bug was not reproducible. Since then there has been a regression.