Migrating app from Dell to HP (Network issue?)

We need to migrate a PC that has a control system application(with a OPC database and MMI package, talking to 40 ethernet-based PLC’s over an TCP/IP network). This PC is one of a twin (warm standby.)

We need to move from a Dell (XP-SP1) to an HP (XP-SP2). Same specs. We used the XP Migration tool (wizard) AND copied our apps over to the HP. Everything looked OK (bench tested stand-alone)until we hooked to the network. The machine then hung (starting our apps) for over 10 minutes, then when finally came up, it could not communicate to the field PLC’s. It seems to be a network issue. Ideas?