The code that you posted works as expected in IE9, FIreFox 10.0 and Chrome 16.0.912.77. My first attempt to format and tab returns properly formatted results. This even works the same after setting the AutoPostBack property to false, so I don't think a lack of postback is the issue.
Have you also tried adding the property: displaydateformat="MM/dd/yyyy"? See Formatting Values
documentation page for insights.
Can you post the entire code for the problematic form pictured in your attachment? This may help to identify the issue.