In your OPEN command, you are setting some of the handshaking things
for a zero timeout, which you probably already know. Are you using the
"old" Serial vi's (not VISA)? The serial port vi's have the
handshaking lines disabled by default. I'd try this: Open up Serial
Port Init.vi, inside there is Serial Port Reset.vi. From there you can
Enable the handshaking lines RTS, DTR, CTS, DSR, etc. Perhaps just
enabling those lines will fix you problem.
It's probably do-able with VISA but I've never tried.
