Just switched over to FF on my Win 10, 64-bit, laptop and trying to configure all the security settings. Out-of-the-box, FF lets me log into this forum with no problems. But as soon as I tinker with the security settings, the forum gives me "A problem occurred. Try again later" when I try to log in.

Anybody know exactly which FF setting is causing this? I can't figure it out and it's driving me nuts...(posting this with IE11)

Thanks!