On some computers, after installing Windows Update agent later than August 2012, Windows or Microsoft Update gets stuck in an endless loop, trying to download page 3 of 3, but it never does. Then the update process restarts and returns to the trying to download part. Rebooting the computer does not resolve the issue.
In my particular situation this issue occurred on Windows Server 2003 with Internet Explorer 8 (same issue is reported by other users with IE7). The solution that seems to work, is to exit the Windows/Microsoft Update process. Not just close the Windows Update window, which simply minimizes it to the task bar, but to actually exit or kill the update process. Then open a new Internet Explorer browser window. From the Internet Explorer Tools menu — select Windows Update. Whatever this option does, it seems to fix the Windows Update endless loop, and from this point on the update agent functions normally.