FaceTalk Keeps Losing Wifi Connection on my iPhone 4

FaceTalk is a great way of staying in touch with friends and family overseas but I have always had problems on my iPhone with it: first speech and video freezes for a few seconds, then it disconnects entirely: that was at home with a BT HomeHub. However, I have just changed my router at home (BT HomeHub 2) and downloaded the latest software for my iPhone 4 and I dont know if one or both of these events is a cause but FT is now no better and actually worse, which is immensely frustrating. Typically when I am in a call things will freeze after one minute, then a minute or so later it will tell me I have lost my wifi connection. However, I go to Settings and choose my router and I immediately reconnect, so this is nothing at all to do with signal strength, which is fine. Sometimes though I cannot reconnect to wifi and I have to make several attempts to do so, sometimes rebooting my iPhone. I have Googled the problem and lots of people seem to be having the same problem, also with iPod, iPad etc. I have tried various fixes suggested but nothing is working. Its intensely frustrating as FT is now a painful and frustrating experience. Hope people wont just blame BT. This doesnt seem to happen when I am surfing the net, just with FT. Any help gratefully received.
iPhone 4 Windows Vista