When I add a particular product to my cart, I cannot proceed to checkout.
When I click "Proceed to checkout" on the shopping cart page, it just redirects me back to the same page.
I do not have any JS errors, nor do I have any errors in my error logs that come up when this happens.
The product is just like many others I have on the site, it's in stock.
I've cleared my caches, reindexed, etc, but nothings seems to work.