Overflow:auto lost when swiching accord tabbox (Safari only)

Fail to switch accordion tabbox in borderlayout, if I specify overflow:auto to tappanel.

Here is the example code,
<borderlayout height="500px">
<north size="50%" border="true">
<borderlayout>
<west size="25%" border="true" flex="true">
<tabbox width="400px" mold="accordion">
<tabs>
<tab label="Tab 1"/>
<tab label="Tab 2"/>
</tabs>
<tabpanels>
<tabpanel height="100px" style="background:yellow">This is panel 1</tabpanel>
<tabpanel height="100px" style="background:blue;overflow:auto">This is panel 2
<div height="200px">---</div>The second panel
</tabpanel>
</tabpanels>
</tabbox>
</west>
<center border="none" flex="true"/>
<east size="50%" border="true" flex="true"/>
</borderlayout>
</north>
<center border="true"/>
</borderlayout>