In addition to upgrading the underlying platform running this site, I thought I was about due for a design change as well.
Now that I’ve fixed my issues with Windows Live Writer and Sitefinity, I can finally take some time to talk about the migration process itself, and hope that it will be helpful to anyone else going through the same process.
When you create a blog in Sitefinity, you must also assign it a Default Page, which is the page that contains the BlogPosts widget for displaying the full Details View of a post.
If you delete this page, move the BlogPosts widget to another page, or modify this relationship in any other way, you must make sure to update the settings for your blog so that it always points to the correct page. Otherwise, Sitefinity will have no way of knowing where your blog posts are located.
I recently updated my website from Sitefinity 3 to 4 in an effort to rededicate myself to blogging and content writing in general (as you probably have already noticed, I suck at writing! more on this later).