Funny Behaviour (scrollpane and jbutton tricking me)

Question

Hi,
I'm close to freaking out. I'm building a GUI that acts as kind of data base editor. There is a combobox to select a table, a scrollpane for viewing and thre buttons to add/remov/edit rows. My test data comes from a Properties object and is transferred into a TableModel in order to create and display the table.
I pick a table from the comobox and the the table is displayed and the buttons are enabled. As soon as the mouse leaves the scrollpane and enters it or one of the buttons again the buttons become disabled and the table disappears. Picking the table again shows everything again, apart from leaving the add-Button disabled from time to time.
There is a method that is called when the user selects no table but the initial "Select a table" item in the combo box. This method is NOT called (there is debug output to indicate this). There is no MouseListener or MouseMotionListener added to any component.
What is this??? Why are sometimes only 2 buttons enabled instead of all three?
This is the event handling code
private void displayCategory(String category){
        // get category data
        Properties data = getTestProps();
        // create table
        ProfileTableModel ptm = new ProfileTableModel(data);
        ptm.addTableModelListener(this);
        // show table
        JTable table = new JTable(ptm);
        table.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
        ListSelectionModel rowSM = table.getSelectionModel();
        rowSM.addListSelectionListener(new ListSelectionListener() {
            public void valueChanged(ListSelectionEvent e) {
                //Ignore extra messages.
                if (e.getValueIsAdjusting()) return;
                ListSelectionModel lsm =
                        (ListSelectionModel)e.getSource();
                if (lsm.isSelectionEmpty()) {
                    System.err.println("GUI no row selected");
                } else {
                    int selectedRow = lsm.getMinSelectionIndex();
                    System.err.println("GUI row #" + selectedRow + " selected");
        profilePanel.displayTable(table, true);
    private void clearDisplay(){
        System.err.println("GUI DISPLAY NOTHING");
        profilePanel.displayNothing();
    public void itemStateChanged(ItemEvent e) {
        System.err.println("GUI ITEM STATE CHANGED " + e);
        if (e.getStateChange() == ItemEvent.SELECTED){
            if (e.getItem() instanceof BoxItem){
                final String cmd = ((BoxItem)e.getItem()).getCommand();
                (new Thread(new Runnable(){public void run(){displayCategory(cmd);}})).start();
            } else {
                clearDisplay();
    }This is the GUI code
    protected void displayTable(JTable table, boolean editable){
        addButton.setEnabled(editable);
        removeButton.setEnabled(editable);
        editButton.setEnabled(editable);
        table.setPreferredScrollableViewportSize(new Dimension(400, 330));
        scroll.setViewportView(table);
    protected void displayNothing(){
        System.err.println("GUI display nothing . . . . . . . . . . .");
        scroll.setViewportView(blank);
        addButton.setEnabled(false);
        removeButton.setEnabled(false);
        editButton.setEnabled(false);
    }Cheers,
Joachim

Answer 1

There is a method that is called when the user
selects no table but the initial "Select a table"
item in the combo box. This method is NOT called
But this method displayNothing() is the only place where buttons are
disabled (at least acording to the posted code fragments).
How can buttons be disabled when this method is not called?
You see, it's difficult to test your code because it is not a self-contained
compilable example.
A short self-contained compilable example often helps you and
others to discover an otherwise mysterious bug.