Problem with forced password changing using policy

Hi!I need some advise how to manage properly password changing via policy. I created an explicit policy and assigned it to number of test people. Set a change interval, and settings to force to change internet password as well. It worked out a weird way - password changed, then in two three days it appeared that old password still intact, then new passwords stoped working, and people had to use old one. Anybody got proper document, how to setup password change properly? Another thing, how to see who have changed passwords and who did not ? Thanks! Attaching a links to screen shots with policy settings.

http://files.ribalka02.ru/links/policy

http://files.ribalka02.ru/links/policy-settings