Hello
Recently I got stuck too from playing with permalinks pattern tags; I searched for help and I found this thread. Seems like the problem hasn't been resolved yet, I shall contribute then. After experimenting many things, I eventually got back my blog, and actually thanks to the tips of "deleting .htaccess and checking mysql databases" I read on this thread.
Please excuse my awkward use of english as I am not a native speaker.
This is aimed at newbies and it's sole purpose is debugging. If you still wants nice permalinks, try this first and you'll decide later. Of course, it isn't the perfect and universal solution, it's just MINE.
So, if you are stuck too with the annoying internal error 500:
First, don't panic. Else you might screw the whole thing and in the worst case may definitely lose all your database.
Go on your FTP server, at wordpress root (where the index.php is located). You should find a file named .htaccess, delete it. Now. If it doesnt appear, try to tweak your ftp software options so as to show ALL files.
Try to reload the main page of your blog. Seems to be back, good. Everything? No. The fun thing begins now.
The problem comes from your mysql database where some tables were screwed up 'cause you changed the permalinks pattern.
So go on your admin dashboard, plugins section. Try to avoid at all cost getting on the permalinks page or you'll be stuck with error 500 and you will have to do the first part again. On the lastest versions of wordpress you should have a plugin for database backup. Activate it, then go to the Manage section and you'll see a "backup" tab at the right end. Do a backup of your database, and save the file on your hard disk. It should be gzipped; open the archive with winzip or winrar and extract the file; open it with your favorite text editor, search for the word "permalink", it should bring you on the line
INSERT INTO wp_options VALUES (34, 0, 'permalink_structure', 'Y', 1, 'the_evil_thing_is_here', 20, 8, '', 1, 'yes') ;
DELETE THE EVIL THING! You should have then:
INSERT INTO wp_options VALUES (34, 0, 'permalink_structure', 'Y', 1, '', 20, 8, '', 1, 'yes') ;
Don't save the file, keep it open and locate the entire wp_option tab contents which should go from
# Data contents of table wp_options
to
# End of data contents of table wp_options
Highlight the whole thing and copy it (ctrl+c)
Connect to your mysql database (phpmyadmin). You'll see a list of wp_thing tables where all your blog contents are saved. You'll see an existing wp_options, don't worry. Search around phpmyadmin for the SQL tab where you can execute SQL code, and paste what you've copied earlier. Execute it. The existing wp_options has been overwritten and everything should be back to normal now; rejoice, dude.
Try to surf around your blog, everything should be back to normal, but...
As I am french, my language got numerous written accents, and unfortunately, the backup plugin screwed all of them up. But this is another problem, the only solution I've found so far is to edit all your posts and comments, but that's a very long process and needs a lot of patience. If you are french and still want to try the whole trick, feel free to mail me on maho_windforce27 at hotmail.com. I'll be happy to help you out.
Hope this helps.
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