Edit wishlist.xml and replace the code

<wishlist_shared_index translate=”label”>
<label>Customer Shared Wishlist View</label>
<!– Mage_Wishlist –>
<reference name=”content”>
<block type=”wishlist/share_wishlist” name=”customer.wishlist” template=”wishlist/shared.phtml” />
</reference>

</wishlist_shared_index>

with

<wishlist_shared_index translate=”label”>
<label>Customer Shared Wishlist View</label>
<!– Mage_Wishlist –>
<reference name=”content”>
<block type=”wishlist/share_wishlist” name=”customer.wishlist” template=”wishlist/shared.phtml” />
</reference>

<reference name=”root”>
<action method=”setTemplate”><template>page/2columns-left.phtml</template></action>
</reference>

</wishlist_shared_index>