Ditto. Still happening for me too. Just to clarify the issue I am having: I uncheck the “Users must be registered and logged in to comment” setting, but it keeps reverting back to checked. It seems to happen randomly. Sometimes it will be ok for a few weeks and revert, sometimes it will take only a day or two to revert.
Here is a list of my active plugins:
-Akismet
-Audio player
-Conditional CAPTCHA for WordPress
-Dashboard Post-it
-fbLikeButton
-Google Analytics for WordPress
-NextGEN Gallery
-Photo Sidebar Widget
-Podcasting Plugin by TSG
-Share a Draft
-Sociable
-Tumblrize
-WPtouch
My theme is “Green Light” by Template Lite.
Please post yours so we can see if there is anything similar that raises a flag.