We have resolve the issue with top menu navigation after upgrade magento to least version. Just recently I get new issue with checkout page that, step 3 Shipping Method is not working after upgrade magento 1.8 with my custom theme. Checkout process is stuck on step 3 Shipping Method.
After exploring web and debugging the code I have found solution. In order to resolve this issue you just need to add new class to html tag fieldset as shown below,
Go to /app/design/frontend/base/default/template/checkout/onepage/payment.phtml
look for the code
<fieldset> <?php echo $this->getChildHtml('methods') ?> </fieldset>
change it to this
<fieldset id="checkout-payment-method-load"> <?php echo $this->getChildHtml('methods') ?> </fieldset>
I hope this would resolve your issue….