DNS .Resove & .NET 2.0 headache??

Question

I can type an IP address and receive Internet domain name and my workstation name however no other IPs of computers on our internal network will resolve to a thier machine name only to the same IP that is entered. What's up Microsoft????

I can say that before we switched over .NET 1.1 to 2.0 the Dns.Resolve(entry); would find a name for any IP, LAN or WAN.

Q. Any ideas??????????

[This is new .NET 2.0 method that replaced the former .Resolve method]

private void LookupIP(string entry)
{               
     try
     {
          IPHostEntry IP = Dns.GetHostEntry(entry);
                                txtBox2.Text = IP.HostName;
     }
          catch(Exception exception)
{