If you have found that you are unable to browse either Companyweb or Sharepoint Central Administration after applying KB 2345304 (MS10-072: Description of the security update for Windows SharePoint Services 3.0: October 12, 2010), then refer to the following blogpost for more information and steps on how to fix the issue:

http://blogs.technet.com/b/sbs/archive/2010/06/18/companyweb-and-sharepoint-central-admin-not-accessible-after-installing-kb983444.aspx