checkpassword and qmail-pop3d

Hiya.

I'm using qmail-pop3d and I suspect that checkpassword is not correctly 
authenticating passwords.
I've implemented qmail-pop3d with the following script (used 
lifewithqmail.org receipe)

#!/bin/sh
exec /usr/local/bin/softlimit -m 4000000 \
/usr/local/bin/tcpserver -v -R -H -l 0 0 110 /var/qmail/bin/qmail-popup \
mail.siegedesign.no /bin/checkpassword /var/qmail/bin/qmail-pop3d 
Maildir 2>&1

It seems like this issue has been discussed several times before 
(google) but I can't seem to find the answer.
checkpassword file downloaded from cr.yp.to is installed as described there.

Thanks for any pointers or hints :)

- Kjell Arne