[Zope] upgrading to 2.1.3 and acl_users

Hi, I have performed an upgrade from 2.0.0 tot 2.1.3. (Windows NT) by copying the data.fs.* to the var directory of the new Zope install. Both services were stopped during copy. All went well, but in all acl_users folders the passwords appear to have disappeared: in the manage screen of acl_users, the password and confirm fields are empty. However, the site functions as it should: where required access is only granted after inputting the original password that belonged to a user in the 2.0.0-version. Does anybody have a clue about what could have happened, respectively whether this is a forerunner of trouble? cb