I recently did an emerge -c, causing /usr/lib/libpopt.so to disappear. I located this file in sys-libs/popt, of which I had version 1.6.3 installed. Re-emerging popt solved the issue. I guess something went wrong when cleaning up the old versions of popt, but naturally, I'm not able to reproduce this... Nevertheless I submit this bug in case it is obvious to see for you guys what went wrong.