This is a bug. The overflow property is not implemented on fieldsets in firefox. Do you have to use a fieldset? If not I would suggest changing it to a div:
Change:
<fieldset style="border-radius: 5px; padding: 5px;height: 450px; border: solid 1px red; overflow: auto;">
to:
<div style="border-radius: 5px; padding: 5px;height: 450px; border: solid 1px red; overflow: auto;">