mac os software update link modify
To reset the software update link to the default run this command:
defaults delete /Library/Preferences/com.apple.SoftwareUpdate CatalogURL
Source: http://support.apple.com/kb/HT4069
Also you can try this:
Move the softwareupdate.plist file out of Library/Preferences to desktop...and run a Software Update again...this will connect to Apple's ASU server and see if additional updates are coming down