I've made a big mistake ! I have launched a full upgrade via package manager on a etch amd64 with the testing repository checked. The installation stops with this message:
E: /var/cache/apt/archives/libc6_2.3.6.ds1-7_amd64.deb: trying to overwrite `/usr/lib64', which is also in package nspluginwrapper Now libc6 appears as broken and there is no way to fix it. Anyone can help ? Thanks Umberto