To find out if it's system wide or user specific, try this...
Open System Preferences>Accounts, unlock the lock, click on the little plus icon, make a new admin account, log out & into the new account.
Does SWUPD work in the new account?
Some other possibilities here...
https://discussions.apple.com/message/3641899?messageID=3641899#3641899?messageI D=3641899