demime.pl related problem

I have "demime.pl" working fine on my list for a while, except once a 
while some spam mail cause this error to appear in a mail to the 
listmaster:

  450 Lynx formatting failed: open3: exec of lynx --stdin
  --dump --force_html --hiddenlinks=ignore --localhost
  --image_links --nolist --noredir --noreferer --realm
  failed at /var/list/bin/demime.pl line 1519

I could't figure out why and I was not really bothered as long as normal 
mailing works fine and the spam is filtered out.  Now something weird 
happened -- upon a normal post by a legitimate user, the Smartlist 
completely replaced the mail body with this error line to have posted to 
the list.

Could anyone help for hints what could be wrong?

FYI - the demime.pl recipe is the very first before all others in 
rc.local:

  :0 fw
  | /var/list/bin/demime.pl -

Thank you,
Zhiliang