changing the password

HI anybody had any problems changing the password of a user once registered?

Using standard theme, the rest of the site works. You can log in and out, but when you change the password, or if I as the admin change the password, nothing changes. Old password stays, or is there a time delay before update becomes a reality?

This has been a problem for a few weeks, I thought the updates would fix this. I have a similar problem in four sites.