These rollup updates address a number of issues in Windows Vista, including some that are directly related to networking functionality.  They also increase stability issues related to graphics and printing, faster resume times from hibernation, and more.  Check out the following Knowledge Base articles for more information and the links to download the updates:

938979: An update is available that improves the performance and reliability of Windows Vista - http://support.microsoft.com/default.aspx?scid=kb;EN-US;938979

938194: An update is available that improves the compatibility and reliability of Windows Vista - http://support.microsoft.com/default.aspx?scid=kb;EN-US;938194

- Michael Platts