https://github.com/esp8266/Arduino/issues/1094
The only difference I can offer is that when I connect to the WAP on one of the physical ports, no problems. I can ping and control the device all day.
Switch my laptop to just WiFi, and all I get are net::ERR_CONNECTION_REFUSED.
I can ping it, but the webserver won't connect.
So Physical to WiFi, good. WiFi to WiFi, bad