Thanks for the post- this plugin was causing the same problem for me.
The problem was with “InlinePosts Plugin 2.1.2.g – by Aral Balkan”. I had it installed and active and had decided that it wasn’t what I needed- it was creating this anomaly. More information can be found on the following thread:
http://wordpress.org/support/topic/167892
And, by the by, the self-closing tag wasn’t breaking my layout. That’s just my own lack of CSS expertise…
