When the kerberos USE flag is set, many packages such as dev-libs/openssl-0.9.8h-r1 net-fs/nfs-utils-1.1.3 pull in app-crypt/mit-krb5-1.6.3-r1 as dependency which in turn pulls in
sys-libs/com_err-1.40.9 and sys-libs/ss-1.40.9. But both are blocked by =sys-libs/e2fsprogs-libs-1.41.2 which is pulled in by sys-fs/e2fsprogs-1.41.2.
So it is impossible to do a emerge -uDN world in a stable x86 system
I can confirm this is a problem. Temporarily unmerging ss and com_err does not help, and revdep-rebuild also runts into this problem. Also, the kerberos flag seems to coming from the default profile, I have not set it anywhere.
The problem has been addressed in >app-crypt/mit-krb5-1.6.3-r1 by changing the dependencies from
||(( >sys-libs/e2fsprogs-libs-1.40.11 ) ( sys-libs/com_err sys-libs/ss ))
but none of these versions have been marked stable, as of this moment.
*** This bug has been marked as a duplicate of bug 234907 ***