Not sure if you have solved the issue yet, still, assuming you want to hide the layered navigation block for filters where there is only one filter to be shown.
In a stock Magento installation, at file location app/design/frontend/base/default/template/catalog/layer/view.phtml
file, you have this block of code :
<dl id="narrow-by-list">
<?php $_filters = $this->getFilters() ?>
<?php foreach ($_filters as $_filter): ?>
<?php if($_filter->getItemsCount()): ?>
<dt><?php echo $this->__($_filter->getName()) ?></dt>
<dd><?php echo $_filter->getHtml() ?></dd>
<?php endif; ?>
<?php endforeach; ?>
</dl>
You'll need to have that file in your theme folder, and the place where it is checking for 0 results, you can simply chnage it to check for atleast 2 results. So the code will become :
<dl id="narrow-by-list">
<?php $_filters = $this->getFilters() ?>
<?php foreach ($_filters as $_filter): ?>
<?php if($_filter->getItemsCount() > 1): ?>
<dt><?php echo $this->__($_filter->getName()) ?></dt>
<dd><?php echo $_filter->getHtml() ?></dd>
<?php endif; ?>
<?php endforeach; ?>
</dl>