Sorry if this has been addressed in this thread already, but it's over 300 pages long and the old needles and haystacks phrase comes to mind.

My problem is when I select the Google Checkout radio button at the final stage of checkout and click "Confirm Order"... I am directed back to The Shopping Cart page.

I have disabled the big blue GC button at the foot of the page as I didn't see the point when all payment options are chosen from the radio buttons. The big blue button does go to Google, but how do I add association between the Confirm Order button button and the GoogleCheckout radio button??