I found a quick fix to the problem I had with several characters displaying incorrectly after I upgraded to WP 2.2. In particular, some apostrophes, quotation marks, and hyphens were now displaying as â€™, and the problem occurred even when I checked old archived posts. The problem was that my posts were not in the latest valid html (UTF8), but when Fantastico upgraded my WP blog it automatically "improved" the wp-config.php file to use UTF8.
Here is the blog post that told me why this occurred and how to fix it:
This is not an ultimate solution, but for now it's great. I'm going to try preparing all my future posts in UTF8 from now on, and just copy and paste them in valid UTF8 html.