dilettanti

The problem is a bad regex in the wpautop function. In /b2-include/b2functions.php, you need to modify line 13 to look more like line 12. About three-quarters through the 13th line of function wpautop, you should see a string something like:
p|h[1-6])>)
Just add a few characters to make it look like:
p|h[1-6])[^>]*>)
(Notice this sequence appears in the 12th line, right above it). That should fix the dangling tags issue in most places, unless you have block-level elements in list items or something similar.

You’re right—when I republish without the class attribute, it works fine. I’m using version 0.72 (just downloaded it on Sunday). I haven’t really had a chance to look at the source yet, so I don’t have much familiarity with how WP works (I’m a long-time MT user).
I’ll take a closer look at wpautop (can’t really do it now, while I’m at work). I definitely need to be able to have attibutes on just about any element. I guess I’ll report back if I figure anything out.
Thanks,
—Michael