Upgrade fails when installing December CU

Update: The issue has been corrected, and a new hot fix package has been uploaded. You only need to re-download the WSS December CU package, which can be found here:

Description of the Windows SharePoint Services 3.0 cumulative update package (WSS server-package): December 16, 2008
https://support.microsoft.com/default.aspx?scid=kb;EN-US;960010