FULL PRODUCT VERSION :
java version "1.4.2_04"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2_04-b05)
Java HotSpot(TM) Client VM (build 1.4.2_04-b05, mixed mode)

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

(This bug is OS independent.)

A DESCRIPTION OF THE PROBLEM :
The problem is that if one clicks on a tree cell and the mouse event's x location is smaller than the last edited cell's real editor's starting x position, then the cell being clicked becomes non-editable to the user. (IsCellEditable() still returns true, but the editor component is not installed.)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
 * Try the following example. After expanding the "colors" tree node, do the
 * following:
 *
 * <UL>
 * <LI> Select the "JTree" node and click on "J" in "JTree" again, "JTree" becomes editable;
 * <LI> Select the "colors" and click on "c" in "colors" again, "colors" becomes editable;
 * <LI> Select the "blue" and click on "b" in "blue" again, "colors" becomes editable;
 * <LI> Select the "colors" and click on "c" in "colors" again, "colors" is NOT editable;
 * <LI> Select the "JTree" and click on "J" in "JTree" again, "JTree" is NOT editable;
 * </UL>
 *
 * <PRE>
 * public class TreeTest extends JFrame {
 *
 * public TreeTest() {
 * super();
 *
 * JTree tree = new JTree();
 * tree.setEditable(true);
 *
 * getContentPane().add(tree, BorderLayout.CENTER);
 * }
 *
 * public static void main(String[] args) {
 * TreeTest TreeTest = new TreeTest();
 * TreeTest.setBounds(200, 200, 200, 200);
 * TreeTest.show();
 * }
 * }
 * </PRE>

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
See "Steps to Reproduce".
ACTUAL -
See "Steps to Reproduce".

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.awt.BorderLayout;
import javax.swing.JFrame;
import javax.swing.JTree;

public class TreeTest extends JFrame{

    public TreeTest() {
        super();
        
        JTree tree = new JTree();
        tree.setEditable(true);
        
        getContentPane().add(tree, BorderLayout.CENTER);
    }

    public static void main(String[] args) {
        TreeTest TreeTest = new TreeTest();
        TreeTest.setBounds(100, 100, 200, 200);
        TreeTest.show();
    }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Replace the default tree cell editor by the following:

  tree.setCellEditor(new FixedDefaultTreeCellEditor(tree,
                (DefaultTreeCellRenderer) tree.getCellRenderer()));


public class FixedDefaultTreeCellEditor extends DefaultTreeCellEditor {
    
    private int lastRowForEditChecking = -1;
    
    public FixedDefaultTreeCellEditor(JTree tree, DefaultTreeCellRenderer renderer) {
        super(tree, renderer);
    }
    
    public FixedDefaultTreeCellEditor(JTree tree,
            DefaultTreeCellRenderer renderer, TreeCellEditor editor) {
        super(tree, renderer, editor);
    }
    
    public boolean isCellEditable(EventObject event) {
        if (event != null
                && event.getSource() instanceof JTree
                && event instanceof MouseEvent) {
            lastRowForEditChecking = tree.getRowForLocation(
                    ((MouseEvent)event).getX(),
                    ((MouseEvent)event).getY());
        }
        
        return super.isCellEditable(event);
    }
    
    protected boolean inHitRegion(int x, int y) {
        if (lastRowForEditChecking != -1 && tree != null) {
            Rectangle bounds = tree.getRowBounds(lastRowForEditChecking);
            
            if (bounds != null && x <= (bounds.x + offset) &&
                    offset < (bounds.width - 5)) {
                return false;
            }
        }
        return true;
    }
}