Well there are no nice pictures in this post, and I admit it is a little bit geeky, but I thought it might help some of the people who ran into the same problems I did, after upgrading to the latest WP version (3.0.1)
Suddenly my website stopped working at all. I got just a blank white page, with no code whatsoever in it. Even the administrative backend stopped working.
After a long time tinkering around with WP source files and after reestoring the database and the WP- configuration for about 100 times (OK, it was two times, but it felt like 100 times 😉 I figured out that it had something to do with the WP-Supercache-Plugin. after I deleted the line “define(‘WP_CACHE’, true); //Added by WP-Cache Manager” in the wp-config.php I finally could log into my admin backend again.
Unfortunately, whenever I opened the plugin configuratio page it automatically added this line to the config file, rendering my blog useless again.
So, now knowing what was wrong, I did some research. Reading the official installation manual (which quite changed since I installed the plugin a lon time ago) I found out, that there ought to be a second .htaccess-file in the folder “/wp-content/cache/” containing the following:
# BEGIN supercache
AddEncoding gzip .gz
AddType text/html .gz
SetEnvIfNoCase Request_URI \.gz$ no-gzip
Header set Cache-Control 'max-age=300, must-revalidate'
ExpiresByType text/html A300
# END supercache
I also figured out, that my WP-folder did not contain a “wp-cache-config.php” file. After copying the example file from the plugin folder (wp-content/plugins/wp-super-cache/wp-cache-config-example.php) and renaming it to “wp-cache-config.php” my blog started working again. Yipee!
I don’t know if I messed things up during the update-process, or if something else went wrong, but now my blog is working again, and I still can use wp-super-cache, which is a great plugin by the way!
As mentioned above, the official WP Super Cache installation instruction helped me a great deal to figure out my problem. You can find it here http://wordpress.org/extend/plugins/wp-super-cache/installation/
I hope this helps. If you have any suggestions please leave a comment!