I have noticed that when the title of the topic contains a single quote; the editor hangs when leaving a reply; by hang I mean the editor does not close and return the user to the forum topic. The comment does post. I have confirmed that it is the single quote in the title because when I removed the single quote from the title (and edited the URL to confirm to the way Dolphin creates the URL to the post) one could then leave a reply to the topic without the editor hanging. This is a problem because users tend to hit the submit button a few dozen times; you know how users are.
Now, I could not recreate this when I made a test on the demo site. However, it does happen on my site. I have updated the forum files to the latest SVN as of today, 9-Feb-2013 and cleared the caches. It did not change the results. Removing the single quote did clear the problem. Perhaps I missed a change in the forum database structure somewhere; could that be the answer; does anyone know?