Garmin Brazil Support send me a solution and it worked perfectly: I've already installed the latest version of: USB drivers, Garmin Agent, Garmin webupdater and Garmin Comunicator plugin 64x. So they asked me to plug the ant+ on my computer and start the Garmin Agent. After that, I should turn off the watch pairing (Menu > Settings > System > Computer > Pairing) for 10 minutes and then turn it ON again. The last step was to deactivate 'pairing new devices' on Garmin Agent and activate it.
