Phil Windley at ZDNet explains as part of his discussion of Landmines at the Patent Office:
If your company uses MS Office (and who doesn’t?) you may soon be deploying a patched version of Office so that Microsoft can get around a patent infringement suit that they lost. Seems that Guatemalan inventor Carlos Armando Amado was granted a patent in 1997 that covers some method that Access and Excel use to exchange data. Because Microsoft paid for $8.9 million for infringements between March 1997 and July 2003, any existing installations of Office 2003 can stand but new installations will need a patched version that no longer infringes.
New Office XP installations need patching too as explained at the second link.