It's also my second one, the first one had trouble with the home button. I don't know if it's on multiple WiFi networks, I'll give that a try. It's happened only a couple of times though, sometimes everything is fine and sometimes it isn't, I feel like it's related to the time since I last restarted it or something. For example yesterday I was at the movies and wanted to look something up on my iPhone and was surprised that there was no 3G available even though I was in a big city. So I restarted it and it connected to 3G immediately. When I got home, it was on WiFi for a while and then I went to a birthday party and when I Wanted to check my Facebook 3G connection was immediately available. It's weird.