I have made an emerge -u world, everything went right, but once the update was complete, I couldn't use emerge anymore (even if i type 'emerge' without options) : root sur locki # emerge python2.2: /lib/libpthread.so.0: version `GLIBC_2.3.2' not found (required by python2.2) I know that the update was on gcc, glibc, emerge and python. But I can't tell you more about this issue...
have you tried running etc-update and env-update?
The problem is that you upgraded glibc at some point, probably by using ACCEPT_KEYWORDS="~x86" - then downgraded glibc, probably by removing those keywords (or switching between them). You can recover from this by grabbing the glibc tarball from http://cvs.gentoo.org/~avenj/bins/ and installing it using the method specified in the README in that directory. Stick to using ACCEPT_KEYWORDS="~x86" after that. For further assistance, please try the forums or the IRC channel.