After following the directions posted previously in this thread, I managed to build a working programming cable. When using a usb-to-serial converter cable, they somehow mess up the handshaking that is going on to put the Vex microcontroller into programming mode. So to fix that, I had to use a microcontroller to generate the correct signal. So my home made programming module has a microcontroller in addition the the RS232 level shifter. You can take a look at the cable and a video of how it works on my site:
www.CrestOak.com. Enjoy!