Following are some useful utilities for handling the good old libraries.
This is sometimes helpful to fix wrong linked libs:
# ldconfig
ldd is helpful to see a list of libraries a binary is linked against.
# ldd /usr/X11R6/bin/glxgears
libglut.so.3 => /usr/lib/libglut.so.3 (0x40014000)
libGLU.so.3 => ...