If you have a conenction error with an Ethernet driver and you have checked to be sure that the IPX TCP/IP address is in the correct subnet and you can ping the PLC and it appears to be functional in all other resepects such as being able to download to the unit there is one other place to check on the new IPX units with two ethernet ports.
It may be necessary to switch the Network port on the IPX (Or any runtime hardware with two ports) that the PLC is plugged into or change which one is set as default in Windows. If it is not the one Windows considers the default port, the driver may be trying to use the other port that is configured as default in Windows.
(Since older units have only one port, it is always default. The IPX has two so it is possible that the port it is currently plugged into is the secondary not default.)
To leave it plugged into the port it is in and change the binding order, here is a procedure from Microsoft to change which network port is default.
http://support.microsoft.com/kb/894564
How to change the binding order of network adapters
1. Click Start, click Run, type ncpa.cpl , and then click OK.
You can see the available connections in the LAN and High-Speed Internet section of the Network Connections window.
2. On the Advanced menu, click Advanced Settings, and then click the Adapters and Bindings tab.
3. In the Connections area, select the connection that you want to move higher in the list. Use the arrow buttons to move the connection.
Notes
The Adapters and Bindings tab lists the connections in the order in which the connections are accessed by network services. The order of these connections reflects the order in which TCP/IP or the next available protocol is bound to the network adapters. The bindings for remote access connections apply to all remote access connections.
The Provider Order tab lists the network providers for this computer. You can use the arrow buttons to change the order in which these providers are accessed. You can arrange the order in which the computer accesses information about the network. Providers and other connections are accessed in the order in which the providers and the connections are listed.