Lateron

Can someone help or explain what is wrong with my wlan configuration? Why can´t I ping my Vu+Duo? I have installed one of the latest versions of Pli (OpenPli20101225) and have got the Wlan connection working with a fixed IP address. I have seen the address on my router´s active list but it disappeared after a few minutes. After a wlan restart on the Vu it was back on the active list but I cannot access it from my PC by pinging or by using a browser. Using Ping, if tells me “Request timed out” or “Destination host unreachable.” I am using a VoNets dongle for my wireless connection. All my other devices, desktop PC, laptop, Samsung TV, printer and scanner are connected to the wireless lan and all work normally. I have checked the subnet setting and the DNS settings many times as well as the gateway value. I have re-flashed the image several times.
Any clues? Why does the Vu or VoNet time out? Is there a parameter I can set to avoid this? Even when the address is visible on the router active list, I cannot ping it from my PC. Is there a “Keep alive (ACK-NAC)” signal that should be going from the router to the VoNets dongle which is not working? The router is an ZYXEL.
Appreciate any help!