Have you unchecked the line below in your /etc/mail/spamassassin/v310.pre? I don't use DCC so I don't bother change mine, but I've read somewhere in the mlist repository saying that. :)
# DCC - perform DCC message checks. # # DCC is disabled here because it is not open source. See the DCC # license for more details. # loadplugin Mail::SpamAssassin::Plugin::DCC
