It has crashed, and now every time an order is placed it's being saved to database as order number 5. EVERY time. :(
You had informed me, via Skype, that you'd only changed the checkout.php and checkout_success.php pages and I'd made absolutely sure that I'd downloaded those before we tested last night. It all worked fine.
This morning I've made some changes, or at least tried to but it isn't working either, to the Tax rules. I've uploaded my cart files, following those changes, and the whole thing has just died.
Hope you can help me establish what's happened here. Thank you.