[Zope] login_form doesn't accept pswd

hi list, I have got this problem with login_form that is driving me crazy... I can create new users with the join_form with no problems (it shows them in the acl_users folder)but when I try to login it doesn't accept the pswd and if I look in the control panel I can see that the pswd is different from the one I created. (suppose I created a 10 letters pswd and in the acl_users folders only shows a pswd of 8 caracters, and always 8...no matter how long is the password I set). It's driving me crazy...can anyone help or anyone else has experienced smthing similar? I'm pretty new to zope and I just created a brand new cmf_site. thanks for helping Luca