This is a good answer; I don't know of any issues where data gets corrupted somewhere between the VISA and Windows Serial API layers so there has to be some difference in settings.
Check the baud rate, data bits, etc. I assume that you're using the exact same setup as far as cable, computer, port, and so on. If this is still a problem make sure that you have the latest version of VISA, or at a minimum tell me what your VISA version is so that I can look into it further. Have you tried using VISA interactive control to do the basic read/write operations? You can access this in Measurement and Automation Explorer under Tools...NI VISA...Visa Interactive Control. Also, I would like to make sure that you're using the shipping example of LabVIEW <-> Serial.vi. Scott B. Applications Engineer National Instruments
