I often say in the forums that the plugin order is important for everything to run smoothly, but this isn't entirely true anymore. A few versions ago, each plugin ran a function at the theme_index_top plugin hook, like this:
If a User page, show user posts,
If a Category page show category posts,
If a Tags page, show tag posts,
If a Search page, show search results,
Nice and logical, right?
Wrong. The problem was that even though