Uninstall that KB update from Add/Remove Programs. Turn off Automatic Updates then goto the Windows Update web site using your Windows Update link in the Start Menu > All Programs list at the top of the list.
Let Windows Update scan your system and recommend any critical/security updates. This should include the Malicious software removal tool. You can hide any other updates you don't want to download/install.
Download that one and once it is installed and completed, re-enable Windows Update in your Security Center. Hopefully that will reset the log.
An alternative if you would prefer not to uninstall any updates is to simply visit the Updates website and let it scan. If it recommends that KB update again, hide it.
See if one of those works.
Running XP sp3 on HP Pavlion XT868 - Windows automatic updater is on, and I see the yellow shield icon, which I click and the installation begins. It completes normally. But then, after a couple of minutes, the yellow shield pops up again telling me there are updates to install. The first time this happened I assumed there were more updates, but as it started I saw it was the same one (malicious software removal tool for March 2009 - same KB number as the last update). Once it started I let it run to completion, again. But, after a few minutes I saw the shield icon again, same update, etc. It seems that the Windows automatic updater doesn't recognize that the update was done. I can turn off automatic updates but then McAfee annoys me with the "Your computer is at risk" messages. Anyone else have this problem, and maybe a solution?