Windows 2000 seems to handle RS232/485 communications differently than other operating systems. To improve serial communications with the 9xxMB I/O, try setting the FIFO threshold levels to Low for both the transmit and receive FIFO's. To do this, use the system icon from the control panel to select "device manager." From the device manager, select ports, then the specific communication port you are using. Now select "advanced.". Move the sliders for both transmit and receive to the Low setting. Make sure this setting has been "applied" and saved. You may need to reset your computer for it to take effect. If this procedure doesn't work, try turning off FIFO buffers, saving, and re-communicating with the module.