All of a sudden, if You unable to access the admin screen of your blog.
When You try to login (<blog-url>/wp-login.php),you dont get an ‘incorrect password’ message but it goes back to the login prompt.
You tried entering the wrong password and that did show You an error indicating incorrect password. Makes You feel like it is not a password issue.
In that case Followiing steps may follow to access Your blog’s admin screen?
Here’s some things to try:
1. logout or logout with http://www.yourdomain.com/wp-login.php?loggedout=true
2. clear cookies
3. exit browser
4. make sure local firewall is not causing problem
5. login with http://www.yourdomain.com/wp-login.php
6. disable all plugins–if necessary read How to deactivate all plugins when not able to access the administrative menus?
If WordPress is installed in something other than the root folder please take that into account for the above url examples
1. Logout using the link above mebtioned
2. clear cookies and restart browser
3. moved plugins directory to a temp directory and created new plugins directory.
4. logged in, and it worked.
5. reverted plugins directory and able to see all plugins again
6.changing the admin user and pass through phpmyadmin and using that.
7.The WP username and password are stored in a MySQL table