During the installation process [ emerge system ] pam-0.75-r4 didn't compile, because it can't find /var/lib/portage/pam-0.75- r4/image/lib/security/pam_userdb*.so
It worked for me and a few other people. Could you try doing an emerge rsync and try building it again?
What version of gcc ?
I have just done everything according to the 'Build from scratch'-instructions at http://www.gentoo.org/doc/build.html , so I don't have a special version of GCC. In make.conf, I selected all USE-options, including the optional lines. Because I have an AMD Athlon processor, I selected the i686 architecture. When I go to the /var/tmp/portage/pam-0.75-r4/work/Linux-PAM- 0.75/modules/pam_userdb directory and run make, it says it is 'skipping this module on this platform'. Disabling the berkdb USE-flag in make.conf does not solve this problem.
Oops, it actually says "This module will not be compiled on this system"
Ok, by running 'emerge db' prior to 'emerge system', I solved this problem. However, I don't know why 'db' doesn't get installed automatically, because it is defined as a dependency in pam-0.75-r4.ebuild