We just applied WSS and SPS SP3 to a production SharePoint installation and it turns out that following the application of WSS SP3 you MAY be unable to open lists and libraries in Data Sheet View! (When I say "may" I mean "will".)

As stated in the KB this is a known issue…

http://support.microsoft.com/kb/923643/

“You may be unable to open the "Edit in Datasheet" view in some document libraries after you install Windows SharePoint Services SP3. Test for this issue before you implement Windows SharePoint Services SP3.”

There is a hotfix for the issue: http://support.microsoft.com/kb/941412

Turns out there are more issues as this blog indicates…

http://sporkbomb.com/2008/04/08/sharepoint-services-20-sp3-disaster/

Anyway, this quick fix appears to be to edit OWS.JS.

http://www.themssforum.com/WindowsServices/Urgent-Edit/ (scroll down to Sept. 27 2007).

I am posting all this in hopes that others will not have to wade through the laundry list of sites that it took to find resolution.