This issue can occur if your serial number got activated on one of the PCI network cards rather than the on-board NIC. To resolve this issue:

1. Uninstall the current version, and select the option to register the uninstall over the web. (Go to Start-> All Programs-> GenArts Sapphire AVX-> Uninstall Sapphire.)
2. Disable all Ethernets except the built-in motherboard: go to the Network Connections Control Panel, and click right on each to see its properties and selectively disable.
3. Download and install the most recent version, and reinstall your serial number.
4. Re-enable the desired Ethernets. Always leave the built-in Ethernet enabled, even if it's not connected to anything.