bogofilter hogging cpu

[MT]

Hi,

I have qmail, vpopmail, courier-imap set up with Debian Woody on a
Pentium 1 (586). Since setting up bogofilter I've noticed the system has
periodically slowed to a crawl. top reveals bogofilter using 40% or more
cpu time.

To setup bogofilter for 2 users I did:

bogofilter -d /home/vpopmail/domains/$domain/$user/.bogofilter -v -s -B
Maildir/.spam

bogofilter -d /home/vpopmail/domains/$domain/$user/.bogofilter -v -n -B
Maildir/.nospam

I call bogofilter using maildrop as follows:

xfilter "bogofilter -d /home/vpopmail/domains/rmtqc.net/mark/.bogofilter
-u -e -p"
if (/^X-Bogosity: Yes, tests=bogofilter/)
{
   exception {
     to "$VHOME/Maildir/.spam"
   }
}

Why is bogofilter hogging so much cpu time? Is there any tests I can run 
to find out more about this problem.

Thank you,

MT