I get corrupted messages, when using SpamAssassin 3.1.1 with spamass-milter 0.3.0. Help!

If you are getting corrupt messages with spamass-milter 0.3.0 and SpamAssassin 3.1.1, where parts of the message header are showing up in the message body, as described in this message, then you're running into this bug in spamass-milter.
Upgrade to version 0.3.1 or later of spamass-milter.