SSH and web interface broken on Yun
It turns out the problem is a fairly common one - Actiontec wireless access points break this way when set to Both, not AES - see https://superuser.com/questions/522781/unable-to-ssh-from-any-wireless-ip-to-another-wireless-ip-on-home-network

Apparently on other routers this bug is marked as a feature, "Wireless Isolation" or something.