When you use Control Panel / Scanner and Camera to select Allow this computer to use a network scanner, you are unable to scan an image.
In Service Pack 2, the Windows Firewall is enabled by default, and it blocks TCP port 21, which is required to be open.
To resolve this issue:
1. Start / Run / firewall.cpl / OK.
2. Select the Exceptions tab.
3. Press Add Port.
4. Type Scanner and Camera Wizard in the Name box.
5. Type 21 into Port number.
6. Select the TCP radial button.
7. Press OK.