Hello,
I am using WP 3.3.1 and have been experiencing this issue on clean multiple installs.
Here is the issue. Comments are turned on by default. After creating a new post the comments work fine.
After editing an existing posts and updating it, the 'Allow Comments' and 'Allow Ping' become unchecked. Checking them and 'Updating' the post does not have any effect (they appear unchecked after the post saves reloads)
I can turn the comments back on for the posts using quick edit.
Any suggestions would be greatly appreciated.
Thank You!