Ok, ci sono arrivato modificando il file index.php del template:
<table class="nopad">
<tr valign="top">
<td>
<jdoc:include type="component" />
<jdoc:include type="modules" name="footer" style="xhtml"/>
</td>
<?php if($this->countModules('right') and JRequest::getCmd('layout') != 'form') : ?>
<td class="greyline"> </td>
<td width="170">
<jdoc:include type="modules" name="right" style="xhtml"/>
</td>
<?php endif; ?>
</tr>
</table>
</div>
<div class="clr"></div>
</div>
<div class="clr"></div>
</div>
in
<table class="nopad">
<tr valign="top">
<td>
<jdoc:include type="component" />
</td>
<?php if($this->countModules('right') and JRequest::getCmd('layout') != 'form') : ?>
<td class="greyline"> </td>
<td width="170">
<jdoc:include type="modules" name="right" style="xhtml"/>
</td>
<?php endif; ?>
</tr>
</table>
</div>
<div class="clr"></div>
</div></td></tr><tr><td><jdoc:include type="modules" name="footer" style="xhtml"/></td></tr></table>
sembra ora che funzioni, che ne dite?