PayPal Express Gateway Not Updating

I've activated the PayPal Express gateway and I can't get it to update my settings. When I click Save Changes, I receive a WordPress Failure Notice with the following message - Are you sure you want to do this? Please try again. I've read this is a WP security error but have no idea how to fix.

I just updated to RC2 as I thought that might be the issue. I've verified the membership tables and all are okay.

Can you help me resolve this issue?