Maybe your system is configured like many distros are so that the dynamic linker (ld.so) does not look for libraries in /usr/local/lib. In that case, you don't get an error from the linker which still looks in that directory, but you get an error in runtime. I'm not sure if this is what your error means and also I can't give a really good advise on how to fix it because just adding /usr/local/lib to the ld.so path (by editing /etc/ld.so.conf and running ldconfig) can sometimes break existing programs which work only with the older libraries installed in /usr/lib.