Spam messages autolearned as ham

[Deeztek Support]

Hello, I'm using the following spamassassin:

SpamAssassin version 3.3.2
  running on Perl version 5.10.1
On Ubuntu 10.04 LTS. I'm having a strange problem with messages being 
autolearned as ham even though they don't score low enough. Here's my 
local.cf config:


use_bayes 1
use_bayes_rules 1
bayes_auto_learn 1
bayes_auto_learn_threshold_nonspam    -0.001
bayes_auto_learn_threshold_spam    9.000
#override bayes default scores
score BAYES_00    0.000
score BAYES_80    3.000
score BAYES_95    4.000
score BAYES_99    4.500

Here's one of the message's in question headers:

X-Spam-Score: 0.257
X-Spam-Level:
X-Spam-Status: No, score=0.257 tagged_above=-999 required=0.6
        tests=[BAYES_50=0.8, DKIM_SIGNED=0.1, HTML_MESSAGE=0.001,
        RP_MATCHES_RCVD=-0.653, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001,
        T_DKIM_INVALID=0.01, URIBL_BLOCKED=0.001] autolearn=ham


As you can see, it scored 0.257 but it autolearned as ham even though 
the bayes_auto_learn_threshold_nonspam is set to -0.001

Am I missing something here?

Thanks in advance