OK - I understand now. Today I downloaded the TMCM-610 USB Driver, connected a USB cable to the 610 board, and installed the driver with the Found New Hardware Wizard. (I am running WindowsXP). I was able to find the board in the TMCL-IDE program (listed as a USB board), and checked the firmware version (it was v6.31). I downloaded firmware v6.35 and installed it successfully on the 610 board. I then sent the command to switch to the RS-232 protocol. I could no longer communicate to the board via USB after this command was sent, so I believe it worked properly. I actually successfully performed these steps on all 4 TMCM-610 boards I am using.
However, I could not see any of the boards as COM ports in the TMCL-IDE program under the RS-232 type. I reviewed the steps you suggested for the other customer in this thread that had the same problem, but was not able to achieve success. In the Windows device manager > driver details, I do not see an Advanced Tab to allow me to select "Load VCP". I also deleted previous FTDI drivers from my computer to be sure to use the latest driver I installed. I also looked in the INF file, but did not see a line already with "Product ID" (to modify to 0xEF10 as you have suggested in this thread). I downloaded the TMCM-610 USB Driver zip file from the TMCM-610 product page. Is this the driver I need? When I look at the driver details it shows FTDI 126.96.36.199 with a date of 10-30-03, which seems fairly old.
For the weekend, I was able to return to control via the regular 610 board RS-232 port and all 4 boards work properly. Do you have any other ideas for me to try on Monday to get the USB virtual COM port working?
Thanks - Gary