One section of products not adding to basket

[Wheels UK]

Hi,

We have many products on our website and recently we have noticed that one section of products are not being added to the basket.

As an example:
Adding this wheel package to the basket works,
http://www.wheels.uk.com/acatalog/al...otz-hanzo.html

However this tyre does not,
http://www.wheels.uk.com/acatalog/tyre-16-205-50.html
this product does not appear to add the permutation in the shopping basket.

These products (all tyres) are set to orderable...
Any ideas?

[NormanRouxel]

Product on http://www.wheels.uk.com/acatalog/tyre-16-205-50.html adds to Cart fine for me.

[TraceyHand]

works fine for me too

[Rich Brady]

And me three