I've recently discovered an issue on my client's FoxyCart checkout page. Every time I try to checkout, I get the same error that the "form was submitted incorrectly." I've tried checking out as a customer and guest, selected different shipping options, tried different addresses, and it still gives me the same error. In the FoxyCart error log, all the tries show up as "Possible CSRF attempt on the checkout page. fc_csrf_id = form" with a string of expected and actual values. The checkout worked fine the last time I tried it a couple months ago, so I'm not sure what is going on.
I'm running FoxyCart version 1.0, integrated into Wordpress 3.5.1 through FoxyShop 4.3.2.
Payment Gateway: PayPal Express
Thanks for your help!