I maintain a blog for my sister at http://abbykingsbury.org/blog -- on Saturday, she emailed me that she was unable to post anything to her blog. I tried to login, typed in her username and password, and wound up with a blank screen at the URI "http://abbykingsbury.org/blog/wp-login.php".
Since I hadn't yet upgraded this blog to 2.1.3, I figured I had nothing to lose by trying that first -- I followed the detailed upgrade instructions (except, of course, I couldn't deactivate plug-ins since I couldn't access wp-admin, though the only plug-ins activated are the Spam Karma, Akismet, and backup plugins). The upgrade appears to have been successful, except I still can't log in to the site.
A few other factoids: (1) After reading http://wordpress.org/support/topic/97220 I looked at the theme. The blog uses a slightly modified Kubrick theme, but I uploaded a standard Kubrick theme via FTP into that folder just in case it was a problem with the theme. Didn't help. (2) After reading http://wordpress.org/support/topic/105933 I checked to see if the blank screen was a browser problem, tried both Firefox and Safari, but same results with both browsers. (3) When I try logging in with an incorrect username or an incorrect password, I get the expected wp-login.php screen telling me "Error: Invalid Username" or "Error: Incorrect password"; when I use the correct username and password, I get the blank screen. (4) Typing in "http://www.abbykingsbury.org/blog/wp-admin/" does not redirect to the login screen, it just gets a blank screen at the wp-admin URI. (5) After reading http://wordpress.org/support/topic/108657, I deleted plugins, but it didn't help (so I uploaded plugins again).
Finally, the error log is full of entries like the following:
[15-May-2007 16:11:10] PHP Warning: Cannot modify header information - headers already sent by (output started at /home/abbyk/public_html/blog/wp-config.php:43) in /home/abbyk/public_html/blog/wp-login.php on line 12
[15-May-2007 16:11:10] PHP Warning: Cannot modify header information - headers already sent by (output started at /home/abbyk/public_html/blog/wp-config.php:43) in /home/abbyk/public_html/blog/wp-includes/pluggable.php on line 313
However, I have already erased and reinstalled wp-config.php (I have not replace wp-includes yet, because if I'm getting errors for wp-config and that doesn't fix it...).
Thanks in advance for any help and advice. Cheers, Dan.