If there's no change, quit the App Store and restore the file you moved from your backup, overwriting the one that may have been created in its place. Otherwise, recreate your settings in the Software Update preference pane.
Hold down the option key and select
from the Finder menu bar. Move the following items from the Library folder to the Trash (some may not exist):
Here, "*" stand for a long string of letters, numbers, and dashes.
If you still have problems, quit the App Store again.
Select this line and copy it to the Clipboard:
Launch the Terminal application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go▹Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Terminal in the icon grid.
Paste into the Terminal window. Depending on which web browser you use, you may have to press the return key. A folder should open. Inside that folder, there may be a subfolder with the name "com.apple.SoftwareUpdate". If so, delete it. You can then quit Terminal.