Sometimes in firefox the headers of Grid don't align w/the columns in the table. Resizing the column fixes it. It seems to happen mostly on the first load of the app, but it's intermittent. Keep hitting refresh and it will eventually happen, generally within a dozen refreshes. Of course, if you demo your app in front of a customer it happens every time

GXT 1.2
Firefox 3.0.4
GWT 1.5.3

package gxt.bugs.client;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.extjs.gxt.ui.client.Style.Scroll;
import com.extjs.gxt.ui.client.data.BaseModelData;
import com.extjs.gxt.ui.client.data.ModelData;
import com.extjs.gxt.ui.client.store.ListStore;
import com.extjs.gxt.ui.client.widget.LayoutContainer;
import com.extjs.gxt.ui.client.widget.Viewport;
import com.extjs.gxt.ui.client.widget.grid.ColumnConfig;
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.layout.FitLayout;
import com.google.gwt.user.client.ui.RootPanel;

public class TableColumnHeaderBug extends LayoutContainer {
public TableColumnHeaderBug() {
Viewport v = new Viewport();
RootPanel.get().add(v);
setLayout(new FitLayout());
setScrollMode(Scroll.AUTO);
List<ColumnConfig> configs = new ArrayList<ColumnConfig>();

for (int i = 0; i < 4; i++) {
ColumnConfig cc = new ColumnConfig();
cc.setId("col" + i);
cc.setHeader("Column " + i);
cc.setWidth(40);
configs.add(cc);
}

ListStore<ModelData> store = new ListStore<ModelData>();
store.add(getTestData());

Grid<ModelData> grid = new Grid<ModelData>(store, new ColumnModel(configs));
add(grid);

v.add(this);
v.layout();
}

private List<ModelData> getTestData() {
List<ModelData> data = new ArrayList<ModelData>();
for (int i = 0; i < 4; i++) {
Map<String, Object> row = new HashMap<String, Object>();
for (int j = 0; j < 4; j++) {
if (j == 2 && i == 0){
row.put("col" + j, "Long value to demonstrate the bug" + i + "," + j);
} else {
row.put("col" + j, "" + i + "," + j);
}
}
data.add(new BaseModelData(row));
}
return data;
}
}