said by JoelC707:
No idea what's up with that. I compared segment for segment, you pinged the right address. Is it because the ICMP firewall rule is set to IPv4 + IPv6? I assumed that was an easy way to add similar rules for both versions to the same host (so you don't have to duplicate a bunch of rules).
Could be a GUI bug (hopefully). Try adding two distinct rules for both v4, and v6.
Edit: I've left an open ping on your WAN address. Will let you know if it becomes pingable.