Contributed By: Cliff Hobbs [MVP SMS]
Reproduced from the Microsoft Software Update Services: Frequently Asked Questions web page:

http://www.microsoft.com/windowsserversystem/sus/susfaq.mspx#top

"This is normally caused by improper detection criteria, combined with the fact that the update is either failing to install each time or succeeding each time but not creating something for which the update detection is searching. If you have computers that suffer from this type of problem, first consult the KB article related to the update to verify that installation is occurring. Then check the SUS public newsgroup to see if the problem is already known."