Communicating with Vex Cortex

Just got the Cortex and downloaded The beta RobotC for Cortex and updated drivers.
Got the message “Bootload failed: Controller failed to respond to autobaud sequence”
Batteries OK. Using Windows 7. Got message whether tethered of WiFi. Also, after a while the Red led (low battery) starts flashing on th controller with fresh batteries?

Any advice?