I've set up a test example for you to see
Go to www.woodware.co.uk
Use the top right login window...
Then click on the yellow text in the top right that says '...Order Basket'
In the middle white section a new button will appear 'Load a previously saved basket'
Click that button to load up the shopping basket.
Now if you try and amend or delete any of the items in the basket and click the 'Update Basket' button (way down at the bottom of the page) nothing will change.
Like I said before I've had to add an awful lot of products to make this error appear, unfortunately this website sells to the trade and so a lot of their customers regularly order this kind of volume!
If it still seems to work, try changing one of the products to a big amount - say a quantity of 30! and then 'Update Basket' again.
Fingers crossed, you can figure it out!