Today I came across an annoying WordPress login error. I had a user who was attempting to log into WordPress after moving the site to a different server, but instead of logging in, WordPress just brought her to a blank page.
The only clue I had was that the site, lets say example.com would go from example.com/wp-login.php to example.com/index.php/wp-login.php on login, and the second page would be blank, while the first page looked to missing some css.
Looks like something was being directed somewhere where it should not have been. My first hunch was to check the .htaccess file, but there was not .htaccess file. Hmm...
After a bit of sleuthing I found that the database table wp_options has a siteurl cell which had a value of example.com/index.php. Changing this to example.com fixed the issue and WordPress began to work as expected.