Spamd startup locale question

[Rosenbaum, Larry M.]

SpamAssassin Server version 3.2.5
  running on Perl 5.8.8
  with zlib support (Compress::Zlib 2.011)
SunOS ornl72 5.9 Generic_122300-07 sun4u sparc SUNW,Sun-Fire-V240

What causes the following error message when restarting spamd?

perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
        LC_ALL = (unset),
        LANG = "en_US"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").

This happens on some, but not all, of our systems running spamd.  All the 
startup files contain

LANG=en_US
export LANG

Thanks,
Larry