[squid-users] Problem with password authentication in 2.5

I'm trying to use password authentication with 2.5 on a Debian unstable box.
Squid itself is working fine, and I've used password authentication on 2.4
successfully so I do have an idea of the mechanism. I don't have any very
sophisticated requirements, and in fact my needs should be met by the samples
in the sample config file. At the moment, in my config file for password
authentication I just have these 6 lines different from my regular config:

auth_param basic program /usr/lib/squid/ncsa_auth /etc/squid.passwd
auth_param basic children 5
auth_param basic realm Squid proxy-caching web server
auth_param basic credentialsttl 2 hours
acl external_users proxy_auth REQUIRED
http_access allow external_users

The first 4 lines above are simply obtained by uncommenting the lines from the
sample config (the first line also had to be completed) - the last two are
quite simple. If I include the lines above in my squid.conf, no clients can
connect to squid. Telnetting to the port simply gets connection refused.

The same applies if I don't even have the acl defined or used i.e. if I simply
have the 4 lines above beginning auth_param in the config file - no squid for
anybody.

So, for the moment I have removed the offending lines. Can someone please
suggest where I'm going wrong?

-- 
Niall