PLEASE READ BEFORE SUGGESTING ANYTHING:
1. I have been to the eShop specific support forums and no one seemed to have any idea what to tell me except to contact my hosting provider.
2. I contacted my hosting provider, and they are saying that they haven't changed anything recently enough to have caused my issue.
3. I have deactivated all other plugins and reverted to the default theme. Did not help my issue.
OK, now that that's out in the open, the "Proceed to Confirmation" button that is supposed to kick customers over to Paypal (the only merchant gateway I have configured) does nothing but reload the checkout page. It keeps the items in the cart, but no one can actually pay me for anything. I've tested this in IE and Opera, deleted caches (no caching plugins used), and even completely restarted my computer. Nothing.
I have set up a $0.01 test item, and would be grateful if anyone would be so kind as to test it and let me know if you're able to get any further than the screen where you input your name and email address, and push the "Proceed to Confirmation" button under the Paypal symbol.