Fresh install of Jenkins through apt-get. Installed and configured the Active Directory plugin. If I add a user directly into the security matrix they can log in fine. If I add a group then when that user logs in they get a 404 error and in the jenkins.log file we see ...

May 11, 2012 8:48:05 AM hudson.plugins.active_directory.ActiveDirectoryUnixAuthenticationProvider resolveGroups
WARNING: Failed to retrieve tokenGroups for CN=John Smith,OU=Department,OU=Company Users,DC=DomainName,DC=local