Upgraded my WordPress to 2.8.1 recently, and after login out of my control panel, couldn’t get back to it to post more.
After entering login info, screen goes blank, and this happens to any of control panel pages, anyway you want to enter, while the blog works correctly.
Read about of a lot of solutions, but the simplest worked best.
With those with a problem alike, simply ftp to your site, rename the content/plugin folder to something, now you can login. Now upgrade your wordpress automatically (it is v3 at the moment). Then rename your plugins folder back to what it was before (“plugin” exactly 🙂 ).
Problem will be solved. log out and log in to check. now you can also update your plugins if you need any.
Update: Your plugins will be deleted, you need to reinstall them, take a list of them before doing that.