Claudia,
Thanks for letting us now about your issue. We have created support ticket 00397233 to support this issue if you want to call in about it. If you'd like to do this, please contact us on the phone line listed at www.prometheanworld.com/.../technical-support-numbers . We have a Spanish line available for your use as well.
Have you tried making sure the USB cable from the board to the computer is less than 5 meters, and is connected at both locations? Please also try taking the USB cable out of the computer, and out of the board, and re-seating them in different USB ports would help.
Also please provide your board's product code, so that we may see the exact hardware that your board comes with. Also, if you have a wallbox, or some kind of termination box that the USB cable goes to from the board, then please bypass that and make a direct connection from the back of the board, to the computer, and then let us know if there is any change.
Please provide your results by responding to this forum post, and then we can continue troubleshooting your issue.
Please let us know if you have any questions.
Thank you,