Program: 32528
Project: 32528
Buggy source:
public MainPanel(){
  super(new BorderLayout());
  table.setRowSorter(new TableRowSorter<TableModel>(model));
  TableCellRenderer renderer=new TableCellRenderer(){
    @Override public Component getTableCellRendererComponent(    JTable table,    Object value,    boolean isSelected,    boolean hasFocus,    int row,    int column){
      TableCellRenderer r=t.getTableHeader().getDefaultRenderer();
      JLabel l=(JLabel)r.getTableCellRendererComponent(table,value,isSelected,hasFocus,row,column);
      RowSorter<? extends TableModel> rs=table.getRowSorter();
      if (rs instanceof DefaultRowSorter) {
        l.setForeground(((DefaultRowSorter<? extends TableModel,?>)rs).isSortable(t.convertColumnIndexToModel(col)) ? Color.BLACK : Color.GRAY);
      }
      return l;
    }
  }
;
  TableColumnModel columns=table.getColumnModel();
  for (int i=0; i < columns.getColumnCount(); i++) {
    TableColumn c=columns.getColumn(i);
    c.setHeaderRenderer(renderer);
    if (i == 0) {
      c.setMinWidth(60);
      c.setMaxWidth(60);
      c.setResizable(false);
    }
  }
  add(new JCheckBox(new AbstractAction("String_Node_Str"){
    @Override public void actionPerformed(    ActionEvent e){
      RowSorter<? extends TableModel> rs=table.getRowSorter();
      if (rs instanceof DefaultRowSorter) {
        JCheckBox cb=(JCheckBox)e.getSource();
        ((DefaultRowSorter<? extends TableModel,?>)rs).setSortable(1,!cb.isSelected());
        table.getTableHeader().repaint();
      }
    }
  }
),BorderLayout.NORTH);
  add(new JButton(new AbstractAction("String_Node_Str"){
    @Override public void actionPerformed(    ActionEvent e){
      table.getRowSorter().setSortKeys(null);
    }
  }
),BorderLayout.SOUTH);
  add(new JScrollPane(table));
  setPreferredSize(new Dimension(320,240));
}

Fixed version (ground truth):
public MainPanel(){
  super(new BorderLayout());
  table.setRowSorter(new TableRowSorter<TableModel>(model));
  TableCellRenderer renderer=new TableCellRenderer(){
    @Override public Component getTableCellRendererComponent(    JTable table,    Object value,    boolean isSelected,    boolean hasFocus,    int row,    int column){
      TableCellRenderer r=table.getTableHeader().getDefaultRenderer();
      JLabel l=(JLabel)r.getTableCellRendererComponent(table,value,isSelected,hasFocus,row,column);
      RowSorter<? extends TableModel> rs=table.getRowSorter();
      if (rs instanceof DefaultRowSorter) {
        l.setForeground(((DefaultRowSorter<? extends TableModel,?>)rs).isSortable(table.convertColumnIndexToModel(column)) ? Color.BLACK : Color.GRAY);
      }
      return l;
    }
  }
;
  TableColumnModel columns=table.getColumnModel();
  for (int i=0; i < columns.getColumnCount(); i++) {
    TableColumn c=columns.getColumn(i);
    c.setHeaderRenderer(renderer);
    if (i == 0) {
      c.setMinWidth(60);
      c.setMaxWidth(60);
      c.setResizable(false);
    }
  }
  add(new JCheckBox(new AbstractAction("String_Node_Str"){
    @Override public void actionPerformed(    ActionEvent e){
      RowSorter<? extends TableModel> rs=table.getRowSorter();
      if (rs instanceof DefaultRowSorter) {
        JCheckBox cb=(JCheckBox)e.getSource();
        ((DefaultRowSorter<? extends TableModel,?>)rs).setSortable(1,!cb.isSelected());
        table.getTableHeader().repaint();
      }
    }
  }
),BorderLayout.NORTH);
  add(new JButton(new AbstractAction("String_Node_Str"){
    @Override public void actionPerformed(    ActionEvent e){
      table.getRowSorter().setSortKeys(null);
    }
  }
),BorderLayout.SOUTH);
  add(new JScrollPane(table));
  setPreferredSize(new Dimension(320,240));
}