After installing a new blog on my server (as an add-on-domain), with it's own database, I can't edit any of the posts on that blog. I tried to replace the complete /admin directory, but this didn't help. Also checked with other installation, but that error 500 keeps popping up whenever I want to edit a post. Changed user permissions for the database, but that didn't work either.
I'm using 3 plugins; Akismet, PhotoQ and Creative Commons.