Multiple MS Charts On The Same Page Use The Same Image Map?

I'm using the Microsoft Chart control to put a couple of charts on a web page. If you render 2 charts, the resulting HTML is something like this (the table is mine, the img and map are from the MS Chart):

<table id="chart">
<tr>
<td id="rolling">
<img src="/ChartImg.axd?i=chart_45ec7063132a47d9bf08ce377f4d6030_0.png&g=d82064ecb0cf459dbda23039ae0c3f70" alt="" usemap="#ImageMap" style="height:200px;width:250px;border-width:0px;" />
<map name="ImageMap" id="ImageMap">
<area shape="rect" coords="190,112,242,132" title="$321.01" alt="" />
<area shape="rect" coords="59,69,111,132" title="$1,017.92" alt="" />
<area shape="rect" coords="138,104,190,132" title="$449.04" alt="" />
<area shape="rect" coords="7,25,59,132" title="$1,714.59" alt="" />
</map>
</td>
<td id="highrisk">
<img src="/ChartImg.axd?i=chart_45ec7063132a47d9bf08ce377f4d6030_1.png&g=6f876c9016cd4b72b5ba60609b9d05ec" alt="" usemap="#ImageMap" style="height:200px;width:250px;border-width:0px;" />
<map name="ImageMap" id="ImageMap">
<area shape="rect" coords="190,128,242,132" title="41" alt="" />
<area shape="rect" coords="59,131,111,132" title="6" alt="" />
<area shape="rect" coords="138,25,190,132" title="922" alt="" />
<area shape="rect" coords="7,121,59,132" title="100" alt="" />
</map>
</td>
</tr>
</table>

Note that both charts use the same name for the image map for each chart - "ImageMap" - and it uses the coords from the first chart on the subsequent charts, even though it puts different titles on each element.

Am I doing something wrong in trying to render 2 charts on 1 page? Is there a workaround for this?