Last night, I decided to take the plunge and upgrade our school's website from WordPress 2.7.1 to 2.8.2. Following the advise of blogs like Karen Blundell's, I backed up the database and deactivated my plugins. The automatic upgrade worked sell. The only glitch was that I use custom permalinks and the control panel could not update my .htaccess file. The result was the 500 Internal Error. Unfortunatley, after giving this file WORLD permissions in the cpanel, WordPress did not correctly update this file for my permalinks. NOW, all I got was a 404 error when accessing any of my blog files.
To solve this, I accessed my blog files via FTP, showing my hidden files. In the /blog directory, I found the .htaccess file, backed it up locally then deleted it. That got me access to the WordPress admin pages again. YES!! From there, I copied the code which was suggested by the Settings > Permalinks page as follows:
RewriteEngine On
RewriteBase /blog/
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /blog/index.php [L]
I placed the code into the .htaccess file and this fixed the problem. SUCCESS!!
As I looked again at the corrupted .htaccess file, I discovered that the code was copied in by WordPress with incorrect line breaks resulting in bad code. It took me some time to figure all this out so solving this issue was a major coup for me. Thanks to the bloggers who covered this issue.