Forcing table cells to stack vertically

By defining a style as follows:

@media aural, handheld {td.layout {display:block;}}

I'm hoping to linearise layout tables when viewed by screenreaders and
handheld devices (it is also be in some selectable user preferences).

This works as intended in Netscape 7 - all the cells stack vertically above
each other nicely, but not in Internet Explorer 6 where the only display
property that td will respond to seems to be 'none'.

I need to keep the layout tables for legacy reasons, is there any way of
doing this and using CSS to stack all the cells vertically in IE?

Thanks
Finn