There is a Linux 64-bit gcc 3.4 version of libpacklib.a which might work on your system. You can download it from
cern.ch/cernlib > Downloads >
PC Linux Cern slc4_amd64_gcc34(Cernlib 2005) > (, compressed tar files “OR” libraries,)
If it does not work, please send details of the compilers on your system to "Heplib.Support@cern.ch".