Server Exception in-between game.

Getting this error while testing game in iPhone with mobile data connection (3G).
Using Realtime SDK v 1.80.

Receive issue. State: Connected. Server: '' Exception: System.Net.Sockets.SocketException: Network is unreachable
at System.Net.Sockets.Socket.Receive (System.Byte[] buffer) [0x00000] in :0
at ExitGames.Client.Photon.SocketUdp.ReceiveLoop () [0x00000] in :0

Not getting this error all the time but sometimes get disconnected because of this error.
Please help.