Hi,
I have some issues on widget renderer when I try to scroll with the mouse wheel.
Some widgets are not rerendering correctly.

here is a simple source code producing the bug :

Code:
import java.util.Arrays;
import com.extjs.gxt.samples.resources.client.Resources;
import com.extjs.gxt.samples.resources.client.TestData;
import com.extjs.gxt.samples.resources.client.model.Folder;
import com.extjs.gxt.ui.client.data.ModelData;
import com.extjs.gxt.ui.client.store.ListStore;
import com.extjs.gxt.ui.client.store.TreeStore;
import com.extjs.gxt.ui.client.widget.ContentPanel;
import com.extjs.gxt.ui.client.widget.LayoutContainer;
import com.extjs.gxt.ui.client.widget.form.CheckBox;
import com.extjs.gxt.ui.client.widget.grid.ColumnConfig;
import com.extjs.gxt.ui.client.widget.grid.ColumnData;
import com.extjs.gxt.ui.client.widget.grid.ColumnModel;
import com.extjs.gxt.ui.client.widget.grid.Grid;
import com.extjs.gxt.ui.client.widget.grid.GridCellRenderer;
import com.extjs.gxt.ui.client.widget.layout.FitLayout;
import com.extjs.gxt.ui.client.widget.layout.FlowLayout;
import com.extjs.gxt.ui.client.widget.treegrid.TreeGrid;
import com.extjs.gxt.ui.client.widget.treegrid.TreeGridCellRenderer;
import com.google.gwt.user.client.Element;

public class TreeGridExample extends LayoutContainer {

    @Override
    protected void onRender( Element parent, int index ) {
        super.onRender( parent, index );
        setLayout( new FlowLayout( 10 ) );

        Folder model = TestData.getTreeModel();

        TreeStore<ModelData> store = new TreeStore<ModelData>();
        for ( int i = 0; i < 10; i++ ) {
            store.add( model.getChildren(), true );
        }

        ColumnConfig cBox = new ColumnConfig( "cBox", "cBox", 20 );
        cBox.setRenderer( new GridCellRenderer<ModelData>() {

            @Override
            public Object render( ModelData model, String property, ColumnData config, int rowIndex, int colIndex,
                    ListStore<ModelData> store, Grid<ModelData> grid ) {
                final CheckBox checkBox = new CheckBox();
                checkBox.setValue( rowIndex % 2 == 1 );
                return checkBox;
            }

        } );
        ColumnConfig name = new ColumnConfig( "name", "Name", 100 );
        name.setRenderer( new TreeGridCellRenderer<ModelData>() );
        ColumnModel cm = new ColumnModel( Arrays.asList( cBox, name ) );

        ContentPanel cp = new ContentPanel();
        cp.setLayout( new FitLayout() );
        cp.setSize( 600, 300 );

        final TreeGrid<ModelData> tree = new TreeGrid<ModelData>( store, cm );
        tree.getStyle().setLeafIcon( Resources.ICONS.music() );
        tree.setAutoExpandColumn( "name" );

        cp.add( tree );

        add( cp );
    }

}
The result optained :

screen_bug_treegrid.png

Thank you