The most likely cause is that there are two files with almost the same name with identical contents, and one should be a symlink to the other, but is not. Here are two files in my
/usr/lib that are OK
libgimpui-2.0.so.0 -> libgimpui-2.0.so.0.800.16
(This symlink is so that programs that look for
libgimpui-2.0.so.0 will find the newer version)
You apparently have
libstdc++.so.5 and a related file such as
libstdc++.so.5.300.0 or maybe
libstdc++.so.6 and their contents are exactly the same. Do
cd /usr/lib; ls and see if this is the case.
Check that the two files are the same, for example do (replace the correct filename in this command):
diff libstdc++.so.5 libstdc++.so.[rest.of.filename]
If they are the same,
diff returns no output.
If and only if they are the same, delete
libstdc++.so.5 and make a symlink to the other file with that name.
sudo rm libstdc++.so.5
sudo ln -s libstdc++.so.[rest.of.filename] libstdc++.so.5
Based on this question on Stack Overflow