That was the message last Wednesday from WSUS. 2505 updates is a lot so I was wondering if maybe a new class or program was added to the updates. Nope, upon further investigation is was ATI Radeon driver updates for Vista.
There was discussion of this in the microsoft.public.windows.server.update_services newsgroup and in the WSUS blog at http://blogs.technet.com/wsus/archive/2007/09/07/ati-radeon-graphic-card-updates-3892.aspx