I've experienced this problem with net-applet from as far back as I can remember. If you attach to only one wifi, there has never been a problem. But, if you use it to connect to multiple locations, it has often failed to connect, or crashes. Recent improvements have helped, but it still occurs for me (at least 6 months ago). Wicd has made stronger connections, and continues to work without crashing, even when no network is available. I do have a problem with it, though. If my computer starts too fast, sometimes the gui starts before the backend is successfully started. So I have to start wicd as root, then stop and start wicd-gtk. But, it has been worth it on my laptop.