The only time such an error should occur is when VISA cannot find the serial port in the system, either because it isn't there (or the operating system cannot open it for whatever reason) or because the VISA Resource Name specified is incorrect. One easy way of assuring that the VISA Resource Name is correct, is by running the "Find Serial Ports" (FindSerial61.vi) that was posted earlier. This will enumerate a list of all serial ports that are available to VISA in your current system. One quick way of checking whether the failure does indeed occur during the open and not in the configuration is to wire a "VISA Open" vi before the "VISA Configure Serial Port" vi. and wire the output "Resource Name" of the Open to the input "Resource Name" of the Configure. It wou
ld be useful to know at which point the failure occurs, so that we can further characterize the problem.