I've had similar problems with CGI::Session. Newer versions use Scalar::Util::refaddr. Older version of S::U won't have refaddr. S::Util is not pure Perl you can't just copy it to a local lib. Either ask the hoster to upgrade C::S (which will in turn upgrade S::U) or use the same version of C::S on your local m/c that the hoster has.

Good luck!