Kaiser,
I see two possibilities here.
1) The sheer data rate of the SM200B is causing problems, or
2) When you installed the software, you also installed the FTDI driver for our SA44B, which is somehow incompatible with the VN-310.
If you re-install the VN-310 driver does it help? If you use FTDI’s “CDM uninstaller” with the VID/PID of the VN-310, and then plug it in, does it help?
