Why is seems like just yestarday we were posting about Update Rollup 3, and here comes Rollup 4!
You can find the KB article here: http://support.microsoft.com/kb/968176
The actual files are here: http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=0ddf8e83-5d9c-4fe7-9ae6-f2713a024071#filelist
Don't forget the updated help files!
One quick addendum, make sure you clear your Internet Explorer cache after installing on both the server and the client side.
