Error in retrieving datas from client

[cmrhema]

Hello,

We are currently using a program where we recieve the details from the client. Developed in C#.It is recieved through sockets.
It is working fine. i.e. When we start the program afresh we do get details properly. We recieve the data as strings and we store in a list box.But after two or three days we have an error stating as below


System.NullRefe renceException: Object reference not set to an instance of an object.
at System.Windows. Forms.ListBox.I temArray.IndexO f(Object item, Int32 stateMask)
at System.Windows. Forms.ListBox.O bjectCollection .AddInternal(Ob ject item)
at System.Windows. Forms.ListBox.O bjectCollection .Add(Object item)
at StepIIServer.Se rver.RunClient2 () in E:\stepII\Serve r.cs:line 346
8/7/2007 8:19:26 PM Error :$<MSG.Info.Ser verLogin>
$DeviceName=352 022000365427
$Software=stepp II_2.4.3_final
$Hardware=STEPP II-55
$LastValidPosit ion=$GPRMC,1452 45.573,A,2941.6 635,N,07659.763 0,E,0.00,2.34,0 70807,,
$IMEI=352022000 365427
$PhoneNumber=
$LocalIP=117.96 .20.147
$CmdVersion=2
$SUCCESS
$<end>
&IMEI=352022000 365427,Distance =63936,
&GPRMC,145240.5 74,A,2941.6635, N,07659.7630,E, 0.00,2.34,07080 7,,
<end>

and another error stating
ping
System.Net.Sock ets.SocketExcep tion: An existing connection was forcibly closed by the remote host
at System.Net.Sock ets.Socket.Rece ive(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags)
at System.Net.Sock ets.Socket.Rece ive(Byte[] buffer)
at StepIIServer.Se rver.RunClient2 () in E:\stepII\Serve r.cs:line 288
8/7/2007 5:51:34 AM Error :&IMEI=35202200 0370849,Distanc e=1487,
&GPRMC,001830.5 15,A,2943.0151, N,07658.9818,E, 0.00,8.79,07080 7,,
<end>

Will you please help

thanks
Hema