ERROR: input must be 8 bytes long at /usr/lib/perl5/site_perl/5.8.0/i386-linux-thread-multi/Crypt/DES.pm line 57.

For me, DES.pm contains:

52: sub encrypt
53: {
54:     usage("encrypt data[8 bytes]") unless @_ == 2;
55:
56:     my ($self,$data) = @_;
57:     return Crypt::DES::crypt($data, $data, $self->{'ks'}, 1);
58: }
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It's that first argument to Crypt::DES::crypt() that needs to be 8 bytes long. I would try inserting a print statement in there - on both the successful and the failing machines. Hopefully, the difference in the output will enable you to determine the cause of the problem (and the solution). Try changing that code to (untested):

sub encrypt
{
    usage("encrypt data[8 bytes]") unless @_ == 2;

    my ($self,$data) = @_;
    print "\nMY DEBUG: ", length($data), " ", $data, "\n\n";
    return Crypt::DES::crypt($data, $data, $self->{'ks'}, 1);
}
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Cheers,
Rob