As of Wednesday, July 4, 2012 at approximately 10:00 UTC, the manifest hashes used on the gentoo-x86 tree will change to "SHA256 SHA512 WHIRLPOOL". To facilitate this change, developers MUST be using at least portage-2.1.10.49 (or portage-2.2_alpha89), or, if your dev-lang/python is built with USE="-ssl", portage-2.1.10.51 (or portage-2.2_alpha95) or later is required.
For users, if they are on a older portage, it will gracefully downgrade. For developers, however, not using a supported version will cause tree inconsistencies. Developers will also need to make sure they cvs up metadata/layout.conf (or cvs up the entire tree) after this change occurs before making any commits. Thanks