If you have the original box the 2412 came in the serial cable is packaged inside the folds of the inside cardboard support. I don’t think it is the cable as the PLM did respond to the initial query to get the type of device. That write/read activity is done inline, before the threads are started. The remainder of PLM responses are posted to a separate thread by the OS.
I do not run window 7. Are there any options that are required/available to run an application as an XP application rather than a native window 7 app.