Hi,
I see no one is replying to you here, which must be frustrating.
The first thought that goes through my mind is that you may be experiencing a UPnP issue with your router. A port request is called and then eventually works, closes, and then takes awhile to trigger properly again. So, if you want something to start looking at as the culprit, your router's firmware and/or settings would be my first guess.
May also be a UDP connection timeout issue with your router.
I would also check your settings against the .pdf guide located at
http://forum.fongo.com/viewtopic.php?f=15&t=16196You may want to look at the KeepAliveExpires value on page 4.
Unfortunately, I'm not entirely positive what could be causing this problem, and I'm mostly just guessing since no one has bothered replying to you, but the first place I would start looking is your router. Maybe check to see if there's a firmware upgrade available.
Others here are far more knowledgeable than I am.
Edited some typos.