Tried to leave a comment, not sure if it is going to show up (the POST was taking an awfully long time). Looks good, but figured I’d toss a few random thoughts out as potential additions.
Something I’ve seen a lot lately are statements like <div class=foo />. Those just seem to wreak havoc. We tend to want to blame them on the wysiwyg editor, but I really don’t know that it is that bad!
For diagnosis, I usually go to the blog in question and then click titles, one by one, to view them in Single view. That’s usually the quickest way to narrow it down to the hosed post. Once I find the post, I’ll validate it and see if that turns up anything useful (mismatched tags, for instance).
If no posts leap out at me, I’ll validate from the main page. If it validates well, or the errors are more semantics than syntax, I might spend a few minutes in View Source and just mentally match up the div tags. It is easy to get a theme hosed up! For instance, editing a sidebar you might forget that the opening div is in another file and add extra divs. Or such silliness (or maybe I’m the only doofus to do that?).
