After upgrading to version 2.1.2 from 2.1.1 my post text was gone and an error from preg_replace() on line 647 appeared complaining about an empty regular expression. I printed the contents of $wp_smiliessearch and $wp_smiliesreplace and they were both empty right before the function call. I worked around the issue by disabling "convert emoticons".
That would be the end of it, but unlike everyone else I've seen on the forums with this issue, I'm not using any emoticon plugins (the error appears even when I disable all my plugins). I would think this is an issue with the 2.1.2 release, but it's been out too long for it to go unnoticed. Anyone know what I'm missing that would fix this?