In case you work on an openSUSE system and you get the following error
$ zypper
zypper: symbol lookup error: /usr/lib/libreadline.so.6: undefined symbol: PC
you can probably "fix" it by setting the 64-bit LD_LIBRARY_PATH like this:
$ export LD_LIBRARY_PATH=/lib64:$LD_LIBRARY_PATH
It worked for me on openSUSE 12.1 "Asparagus".
Credits
Thanks to JRSETI's Blog.