Why can't I login?????

Can anybody tell me why I can't login. Every time I attempt to login
(userid and password are correct), always get "You Are Not Registered
Or Not Logged In". Also can't get into settings to change my password.
(Must use the one you get in email). Can still post replies using my
userid and password. About three days ago, registered and was about
to change password and made some postings. The next night, could not
log on using my password. The system was showing me as an administrator
who first registered in 1969 (neat trick). Any thoughts.