Try to upgrade manually following the instructions on this link:
1. Download the latest Boxee Box firmware at http://www.boxee.tv/download/boxeebox. The downloaded file will be named boxee.iso, and that name must be retained.
2. Copy the boxee.iso file to a thumb drive. Make sure to properly eject the thumb drive after copying the file.
3. Power down the Boxee Box.
4. Power on the Boxee Box by pressing and holding the power button for 5-10 seconds. The Boxee Box will then reboot with the logo in orange.
5. After the Recovery Menu appears, connect your thumb drive to the Boxee Box, wait 2 seconds, choose Reset all Settings and then select Upgrade from USB from the menu, and follow on-screen instructions.