Okay, then you might
have to step a little-bit away from "package land" to diagnose this problem.
(1) Type:
set | grep LD to see if the environment-variable
LD_LIBRARY_PATH is defined. Linux will consult this to see where library-files are.
(2) Type:
less /etc/ld.so.conf. This is a list of directories,
in addition to /usr/lib, /lib, where libraries can be found.
(3) Type:
locate libc.so to see where the files such as the one you seek actually are. (If necessary, as root, run
nice /sbin/updatedb & .. notice the "&" .. to launch the
locate-database update program in the background to make that information up-to-date. You can log-off root once you've launched it.)
This should be enough information to let you resolve the problem. The way that I'm reading it so-far, there are
two possibilities. One is that the wrong version of
libc is installed; the other is that the package database is wrong and needs to be rebuilt. I'm basically exploring the first possibility.