I've noticed recently that on my system longpoll isn't working from the internet. I usually use chrome browsers at home and at work (and on my phone). Longpoll works ok from home over LAN but from the internet icons/readings aren't updated. Even on my phone GPRS connection = Longpoll not working, as soon as i get home WIFI = Longpoll working. I havn't had need to access fhem from work for a while so i'm not sure when this happened. I'm sure it used to work so i did a fresh install of 5.5 and longpoll worked from LAN and internet ok. After an update Longpoll stopped working again.
I have other web servers on my Raspberry pi (webmin, apache) but thought that if these were interfering then the fresh install wouldn't work also.