SMB Authentication Module and Squid

I'm trying to install the SMB Authentication module for Squid, and while
the module looks good, Squid doesn't seem to be attempting to authenticate
against it. Testing the module:

dopey ~ % smb_auth -W MYDOMAIN -B 192.168.0.255
baduser badpass
ERR
gooduser badpass
ERR
gooduser goodpass
OK

And I've added the following lines to squid.conf and restart:

authenticate_program /usr/local/bin/smb_auth -W MYDOMAIN -B 192.168.0.255
acl allowed-smb proxy_auth
http_access allow allowed-smb

But when actually testing it with a browser, I just get "access denied"
and that's it - no login prompt or anything.

The configuration is:

- Samba 2.0.3, installed in our FreeBSD 3.0 machine in /usr/local/samba
and compiled with the patch from the SMB auth module homepage.

- Squid 2.1 Patch 2 compiled with --enable-snmp

I have a feeling I'm missing something on the Squid side, but have read
both the Proxy Auth section of the FAQ and Arjan's page, and everything
seems to be in place. Any ideas? thanks in advance.

--
"Your illogical approach ... does have its advantages."
				-- Spock, after being Checkmated by Kirk