We need more information to help you in your troubleshooting process. Do you have DCA/NCA logs retrived from computers experiencing the problem? Is this problem limited to a single DirectAccess entrypoint or all? is this problem concerns Windows 7 and Windows
8? Do you have special events on DirectAccess Gateway when users are experiencing the problem?
BenoitS - Simple by Design http://danstoncloud.com/blogs/simplebydesign/default.aspx