Perhaps try a repair install of ASU. Although it's for a different issue, there's instructions on how to do a repair in the following user tip:
- Right click on Apple Software Update in the Start Menu and bring up the Properties Window
- Select the Security tab
- Select your Username (don't worry about what rights the computer Administrators group has, it does not apply here) and select Edit
- After you pressed Edit, you should have a Window that shows all the computer groups (Administrators, etc.) and usernames (yours and other users (if any)) on your computer. Select yours.
- Change your Rights to Full Control, press OK.
- Press Apply, applying the changed settings to Apple Software Update, then press OK to close the Properties Window.
You can now run Apple Software Update and see what programs (updates) there are to download. For some reason, the latest update which came down gave the computer user (in this case, you--meaning pitiful us) no rights other than deleting. This meant that we could not see anything--no updates, nothing. What we just did through this list was give the ability back to the user.