[sanddrag]

You need to use the Vex Cortex firmware upgrade utility and actually give them a call on the telephone during business hours when it says Invalid ID and asks you for a code. They'll give you the code over the phone, and you'll be back up a running right away. This issue is very frustrating and something that Vex needs to fix. I've had it happen on two Cortex controllers. I should never have to call someone during business hours to download code to my robot. In the educational environment for which this product is intended this is a nightmare.

As for tethered vs. wireless, if you're using RobotC you might need to make sure the "VexNet communication mode" is set to "USB Only" in order to run free of the cable. Also, I've had four VexNet USB keys fail that I have sent in for return. I also had one Cortex with a bad solder joint where the USB riser board attaches to the main board.