I have not come across the problem but think I can take an educated guess at the cause and way round it. The update being applied by WSUS (god bless it) is security hotfix MS08-040, see this link

http://www.microsoft.com/technet/security/bulletin/ms08-040.mspx

and in particular the FAQ section.

Hotfix 2148 does not include this security patch that for you has been directly applied to SP4, so you need to apply the QFE update of MS08-040 post patch level 2050, which will bring you up to to 2273 and include the 2148 hotfixes you require. So you need to download the contents of KB948111 from

http://www.microsoft.com/downloads/details.aspx?familyid=8316BC5E-8C2D-4710-8ACC-B815CCC81CD4&displaylang=en

Thats my take on it anyway and I hope I explained that clearly!