I recently upgraded to WordPress v2.6. After a quick check, everything seemed to work fine. However a few minutes ago a reader of this blog told me that he encountered some problems: The overview would work, but everything else like reading certain posts, commenting or using the RSS feed produces a “404 – not found” error. I quickly found out that the blog was experiencing bug #7306. The suggested workaround, filling the category and tag fields under wp-admin -> Settings -> Permalink, worked instantly and now everything should be up and running again. Let’s hope WordPress v2.6.1 will be released soon to fix the problem without the need for workarounds.