Desine time XAML serialization problem in VS2010 Designer

Question

The wired problem is, in VS 2008, everything works fine. In VS2010 while serializing, it is missing the "ReportDimensionElements" so I'm unable to get the values back from the serialized value back from the XAML. It says, "'ReportDimensionElements' is null" am I missing anything silly.

Note: I have marked the ReportDimensionElements class with [DefaultValue(null)] for avoiding {x:Null} being serialized. Will it be causing this by any way?

Serialized XAML

.Net 3.5

<Report>
  <Report.CategoricalAxis>
    <CategoricalAxis>
      <CategoricalAxis.ReportDimensionElements>
        <ReportDimensionElements Capacity="4">
          <ReportDimensionElement DimensionName="Customer" HierarchyName="Customer Geography"        LevelName="Country" />
        </ReportDimensionElements>
      </CategoricalAxis.ReportDimensionElements>
    </CategoricalAxis>
  </Report.CategoricalAxis>
</Report>

.Net 4.0

<Report>
    <Report.CategoricalAxis>
        <CategoricalAxis>
            <CategoricalAxis.ReportDimensionElements>
                <ReportDimensionElement DimensionName="Customer" HierarchyName="Customer Geography" LevelName="Country" />
            </CategoricalAxis.ReportDimensionElements>
        </CategoricalAxis>
    </Report.CategoricalAxis>
</Report>

Great Thanks