WP Version 3.7.1
WP E-Commerce Version 188.8.131.52
I am having a similar problem. My site has used WP E-Commerce successfully for a long time. Something has broken within the last week - and I have not made any edits or updates.
My checkout page is also "refreshing" when the purchase button is clicked. I am using PayPal Payments Standard 2.0. My last successful order was placed on 12/3. I have an incomplete order on 12/4 and now customers are telling us that nothing happens when they click 'purchase'. I have tested it with the test gateway and it is doing the same thing. Both the test gateway and PayPal checkouts worked as of a month ago when I tested after updating.
I have had to resort to hiding the "Add to Cart" buttons and customers are placing orders with a contact form until the issue is resolved.
The plugin worked perfectly for so long - I'd really like to get it working again.