/usr/lib/libstdc++.so.6: version `GLIBCXX_3.4.15′ not found
I’m compiling gcc 4.6 from source, and apparently sudo make install didn’t catch this one. I dug around and found gcc/trunk/x86_64-unknown-linux-gnu/libstdc++-v3/src/.libs/libstdc++.so.6.0.15 I copied it in to /usr/lib and redirected libstdc++.so.6 to point to the new one, and now everything works.