[Serusers] connection being dropped

Hello, Have any of you had an experience with Grandstream BudgeTone phones? My outgoing calls are being dropped after 16 seconds. My system looks like this: Grandstream phone ---> SER sip proxy ----> VEGA 50 SIP gateway. x-lite softphone ----> When i make an outgoing call from my softphone it works fine. But not with ip phone. After 16 sec. my VEGA gateway disconnects the call. After talking to VEGA customer support they told me that my ip phone is not replying back to VEGA's ACK requests, and eventualy after 26 sec. VEGA dropps the call. Does anyone out there have a similar setup or ever experienced such a problem? I am running the latest firmware on my ip phone. Srbo Cvetkovic | CityNet, Inc. srbo(a)city-net.com | Pittsburgh, PA voice: 412.481.5406 | fax: 412.431.1315