Magento error "You cannot define a correlation name more than once"

solution:

This is a layered navigation error.

In your catalog.xml search for

"layer_view" . If you find two  occurences for this, then remove one that you don't need.

I commented the second one that I didn't needed and fixed the error.

<reference name="right">

             <block type="catalog/layer_view" name="catalog.leftnav" after="currency" template="catalog/layer/view.phtml"/>

         </reference>

<!--        <reference name="left">

            <block type="catalog/layer_view" name="catalog.leftnav" after="currency" template="catalog/layer/view.phtml"/>

        </reference>-->