Mrtg - How fix

Hello all! How can fix trouble. This is log after install:
-----------------------------------------------------------------------
ERROR: Mrtg will most likely not work properly when the environment
variable LANG is set to UTF-8. Please run mrtg in an environment
where this is not the case. Try the following command to start:

env LANG=C /usr/bin/mrtg
-----------------------------------------------------------------------
Tell me some thing work . Thanks

It says exactly what command you should run: env LANG=C /usr/bin/mrtg

#env LANG=C /usr/bin/mrtg /etc/mrtg
Subroutine SNMPv1_Session::AF_INET6 redefined at /usr/lib/perl5/5.8.8/Exporter.pm line 65.
at /usr/bin/../lib/mrtg2/SNMP_Session.pm line 594
Subroutine main::AF_INET6 redefined at /usr/lib/perl5/5.8.8/Exporter.pm line 65.
at /usr/bin/mrtg line 97
Use of uninitialized value in pattern match (m//) at /usr/bin/../lib/mrtg2/MRTG_lib.pm line 555.
ERROR: "WorkDir" not specified in mrtg config file
I try in /etc/mrtg.mrtg.conf daclarate
WorkDir but it's no work