After I did a "emerge --sync" today, "emerge -pvuDN world" showed the following package conflict:

[ebuild     U ] sys-fs/e2fsprogs-1.41.2 [1.40.9] USE="nls (-static%)" 4,263 kB
[ebuild  N    ] sys-libs/e2fsprogs-libs-1.41.2  USE="nls" 479 kB
[blocks B     ] sys-libs/ss (is blocking sys-libs/e2fsprogs-libs-1.41.2)
[blocks B     ] <sys-fs/e2fsprogs-1.41 (is blocking sys-libs/e2fsprogs-libs-1.41.2)
[blocks B     ] sys-libs/com_err (is blocking sys-libs/e2fsprogs-libs-1.41.2)
[blocks B     ] sys-libs/e2fsprogs-libs (is blocking sys-libs/ss-1.40.9, sys-libs/com_err-1.40.9)

There is a pretty good discussion in Gentoo Bugzilla.

Actually, I just did the following to resolve the conflict:

# emerge -C ss com_err e2fsprogs e2fsprogs-libs

Then "emerge -pvuDN world" complained no more.