products not adding to cart

i am in the process of upgrading my old 1.2.6 site to the new 1.3.7 however i have come across a stumbling block and it appears products are not adding to the card. Am i being totally stupid please take a look at http://www.ukcelticjewellery.co.uk/new/index.php?main_page=product_info&cPath=7&products_id=510
and try adding a product to the cart i have no idea why this is happening.

Any help much appreciated.
Rachel

Since I can add the same product from the Product Listing to the shopping cart ... but not from the Product Info ...

I would have to think either:
1 the product _info page has a malformed form tag ...

2 the product _info page has a sidebox showing with malformed form tags ...
Test by turning off the left column ... can you add?
Test by turning off the right column ... now can you add?

3 Switch to Classic ... now can you add?
If so, the error is in one of your template and override files ...

Hi I have
tried all those things and I still have the problem
I have now seem to have anther problem if i turn on the Display Multiple Products Qty Box Status and Set Button Location and then try to add a product I get the following error

Warning: Variable passed to each() is not an array or object in /home/ukceltic/public_html/new/includes/classes/shopping_cart.php on line 1708

Warning: Cannot modify header information - headers already sent by (output started at /home/ukceltic/public_html/new/includes/classes/shopping_cart.php:1708) in /home/ukceltic/public_html/new/includes/functions/functions_general.php on line 44

Any ideas
Thanks Rachel