Yes, it is another security patch for IE. If you installed the update through Software Update, it should be fine. If you updated it manually (by downloading the package), it will be fine but the Software Update may not realise you have already updated if the package isn't in the Library/Reciepts folder, which would mean that even though you have updated, Software Update just doesn't know it.
Also, you might have this problem if IE is kept anywhere other than in /Applications/
I checked MS's site, and it is apparently a fix for an IE bug that meant a site could crash explorer by sending long directory structures to the browser.