Dropping emails with score of 0

[cptech]

Within the last week some emails (both legitimate and obvious spam) are getting dropped with a score of 0. Dropping Super Spam is turned off.
All the settings are default. Threshold is 3.0.

I've even tried this old trick and still the same thing.

sa-compile -D --list

and then

/etc/init.d/spamassassin restart

Any ideas?

Build:9.1.1~svn20111222r30591release9.1-1lenny


I'm going to try updating it tonight to latest version.