Just want to pass on some information. It appears as though with WP2.5, a field called guid is being set differently than before.
In 2.4 and earlier, the content of this field would be the same as the perma-link field.
While not major, some feed readers are using the guid tag instead of the link tag to grab the perma-link to the post.
What this means — if you see a request to my.blog.com/path/?p=123 instead of my.blog.com/path/perma/link/structure/post-slug , its affecting you.
This is the intended behaviour of WordPress 2.5+, however, it is different behaviour than previous versions. There is no way to correct this problem from within the WordPress interface. The only way to change the format back is via a database edit (look for your post, then column, guid, and set it to the full link).
What is more annoying is that this only happens when you use the WordPress editor. When you use an external editor (like in my case, Windows Live Writer), it gets set the same as it would have in 2.4. It also means I can’t make short little posts from work anymore because I only have the WP editor available there.