The load average always hovers around 20.0 and top shows spamd is culprit. Also, I have trained over 10,000 each of spam and ham and also
You probably have too many spamd children running. With only 512M you probably want 5 children or less.
Sometimes when there is heavy load we get in logs, Cannot open bayes databases /var/bayes/bayes_* R/W: lock failed: File exists
Lock timeout, some message didn't get a bayes score. This is a side effect of the high load average.
Loren