Where, oh WSUS, have you put the DST patches?
Having problems finding the DST patches in WSUS? They're categorized under Update Rollups, which is not one of the default categories. You'll need to enable its synch with Microsoft first.
More info on Susan Bradley's SBS blog: http://msmvps.com/blogs/bradley/archive/2007/02/27/where-are-dst-patches-in-wsus.aspx
Microsoft has a knowledgebase article with the VBScript code for doing the Windows O/S changes manually: http://support.microsoft.com/kb/914387