Facebook app payments stop working after changing SSL certificate

Facebook app payments stop working after changing SSL certificate

My SSL certificate is due to expire in 10 days. I'm using AWS and a load
balancer that forwards HTTPS (port 443) to port 80 on my application
servers.
I uploaded a new certificate to AWS, and I can switch freely between them.
When I visit a test page, I get no problem with either certificate:
https://lb1.cloudstonegame.com/test.html
However, when I enable the new certificate on my live servers, the
Facebook payment window in my application
(https://apps.facebook.com/cloudstone/) stops working. I get this error:
The app you are using is not responding. Please try again later.
On my staging server, everything works fine with the both certificates
using test payments. The same code is running on both staging and live.
Any ideas? Is there some cache on Facebook that I can try to flush? I'm at
a loss.