[tartaglia]

This was a mess back when I first started using X-Payments in Jan 2013. Even QT couldn't figure out what IP was supposed to be in the "X-Payments Call back" field, they ended up doing a trial and error until they got one that worked. I believe it ended up being the IP of my X-Cart installation, which was the complete opposite of what you would reasonably expect , but that what worked and has worked ever since.

Hope that helps, aaaargh.