Column Spanning and IE

[Raymond <support@bigriverinfotech.com>]

docbook-dtd-4.5b1, docbook-xsl-1.69.1, jdk-1.5.0_4, kubuntu-5.04, oXygen-6.1, 
saxon-6.5.4

The following code fragment:
-------------------------------------------------------
<informaltable id="foo" frame="topbot" rowsep="0" colsep="1" pgwide="1">
      <tgroup cols="4">
         <colspec colwidth="4*" align="center" colname="c1"/>
         <colspec colwidth="7*" align="center" colname="c2"/>
         <colspec colwidth="1*" align="center" colname="c3"/>
         <colspec colwidth="1*" align="center" colname="c4"/>
         <spanspec namest="c3" nameend="c4" align="center" spanname="c3c4"/>
         <spanspec namest="c1" nameend="c4" spanname="c1c4"/>
         <tbody>
            <row>
               <entry>
                  <emphasis role="strong">foo1</emphasis>
               </entry>
               <entry>
                  <emphasis role="strong">foo2</emphasis>
               </entry>
               <entry spanname="c3c4">
                  <emphasis role="strong">foo3</emphasis>
               </entry>
            </row>
         </tbody>
      </tgroup>
   </informaltable>
--------------------------------------------------------

Stringparms:
--------------------------------------------
use.extensions 1
tablecolumns.extension 1
make.valid.html 1
html.cleanup 1
------------------------------------------

correctly spans and centers text in cols 3 and 4 in Firefox, Opera, Konqueror 
but NOT Internet Explorer.

Any ideas for IE?

Raymond