You should run ldconfig after making changes to the file. /usr/lib does not need to be in there, as it is one of the standard directories which is hardcoded in the linker.This might be too obvious, but do you have /usr/local/lib in your /etc/ld.so.conf ?No, only these: /usr/X11R6/lib /usr/lib/atlas I tried putting /usr/lib /usr/local/lib into the file and that made no difference.
Rgds, Torsten