Can’t login anymore

I have installed WP 2.9.2 in my server and I was using it normally. The, after a few days, suddenly I couldn’t use the admin, it was on the login screen and I couldn’t log in anymore.

I did reset the password in the mysql database thru phpmyadmin and it worked.

Today, I tried to access the admin and the same thing happened, it was asking for my password but it didn’t worked. But, this time, the password reset didn’t worked either.

I deleted the cache, cookies but still didn’t work. I tried to edit the functions.php from the current theme and nothing.

The weird thing is: There is no error message. When I use a wrong username or password, I get the wrong user/password error. But if I use the correct data, it simply reloads the page.

Any clue on what’s going on? Thanks!