Simple proxy authentication using squid-Collection of common programming errors

I’m trying to configure squid to require authentication.

I’ve got squid to work without authentication, than I

 htpasswd -c /etc/squid3/passwd foo

after this, I’ve replaced

http_access allow all

with

acl foo proxy_auth REQUIRED    
http_access allow foo
http_access deny all

and added

auth_param basic program /usr/lib/squid3/ncsa_auth /etc/squid3/passwd
auth_param basic credentialsttl 30 minutes
auth_param basic casesensitive on

to /etc/squid3/squid.conf.

Now, when I do service squid3 restart, I get

stop: Unknown instance:
squid3 start/running, process 12256

when I run ps aux I can’t find squid amonst processes running and the server cannot be connected to.

Why isn’t this working?

UPDATE

squid3 -d 10 shows:

Can't use proxy auth because no authentication schemes are fully configured.
FATAL: ERROR: Invalid ACL: acl foo proxy_auth REQUIRED