Page not found - listing Hikashop 1.5.3 + J 1.7

After upgrading to Joomla 1.7 and Hikashop 1.5.3 whenever we try to add a product the the shopping cart the pop-up box appears but no product is added to the shopping cart.

When we click proceed to checkout on the popup message sometimes you get the pop-up box saying 'the cart is empty' and 'product added successfully to cart' in the same popup message:

Then at other times if you try again, you get a 404 error "Page not found : listing". The URL it tries to redirect to is www.fairweatherdesign.com.au/uniquefinds/product/listing

(the online shop URL is www.fairweatherdesign.com.au/uniquefinds )

Similar issue occurs if we change the "After a product is added to the cart.." setting to a different option.

Hello Nicolas and thank you for your interest in the matter, I have the business version of hikashop installed and have a similar issue, in this case I have a 404 error whenever I click on the cart button to see what's inside, the products are correctly inserted into it.
I have also an essential version installed in another server but it works correctly, do you have any hint?
Thank you very much in advance!

Hello Nicolas, thank you for your reply!
I realized that it was some kind of "misunderstanding" between the component I use to manage the sef url and hikashop, as soon as i and reactivated it everything was fine.
Thank you anyway for your help, always appreciated

R.

PS: The component is sh404 sef.