Squid proxy server fails to start if I specify ACL for proxy_auth

Actually I'm facing this problem on Windows, but am posting here because there are no forums/mailing list for windows users of squid.
If I add the line
acl password proxy_auth REQUIRED
to squid.conf, then I'm not able to start the Squid proxy server. There is no error message of any kind, it just says failed to start. There is no log file written.
I also tried specifying the username, with the same result:
acl password proxy_auth username1

Elsewhere in the conf file I have specified the external program to use for authentication:
auth_param basic c:/squid/libexec/ncsa_auth c:/squid/etc/passwd

Please help before I shoot myself.

dear
can u share the hardware/software conf. along with the softwares running on proxy server.