[squid-users] SQUID NTLM pop up password

Hello all,

I just installed Squid 2.5stable2 using NTLM Auth. (Linux Slackware 8.1,
kernel 2.4.18, Samba 2.2.8)
The authentication is working fine, I'm making control of users group
that can login, etc...
But one problem is making me crazy:
Sometimes, without reason, a permited user gets a pop up on screen
asking the password... but if him only push ESC, without pass any login
or password, continue browsing perfectly... and after sometime the pop
up back again...
Do you know what can causing that? Any kind of parameter, password
expiration,configuration mistake, bug ... ????
.
Thanks.

-- 
Igor Luiz Oliveira de Souza
Magiclink Solucoes Internet
Analista de TI
Salvador / BA   -  Brasil