Attempting to open terminal server with no network connection

We are using Digi One terminal servers with Realport drivers to make them appear as normal serial ports.
If we try to open a port without a network connection the software behave differently depending on whether we are using Windows XP or Windows 7. On Windows XP the open function (CreateFile) fails immediately. On Windows 7 the open function does not return until the network connection is restored. The port is then opened sucessfully.
Is there any way this behaviour can be altered as it is currently giving us a problem running our application under Windows 7.