title: Vaadin 6.8.9 table improperly display
body: <p>I'm using Vaadin 6.8.9. Recently, I come across a issue. The table doesn't present properly as follow image. The headers are not able to appear. I tried to re-install tomcat7,and compile widgets couple times. The issue is still there. The issue only occur on my machine. I couldn't figure out the problem. 
  Could anybody have this issue ever? Give me some clues. Thanks very much. </p>
  
  <p><img src="https://i.stack.imgur.com/aWv1l.png" alt="Vaadin 6.8.9 table"></p>