Recently, Diego added sys-libs/pam-0.99.6.3-r1 to portage, which removed pam_stack. mod_auth_pam's config file still uses pam_stack so it should be updated. I've attached the corrected apache2.pam to be included in the ebuild's files directory. Thanks!
Created attachment 101850 [details] Updated apache2.pam
Thanks to you (and Jakub), I just fixed it in CVS. It's gonna need about an hour till it will show up on you're favorite rsync-mirror! Thanks.