Comment Order Not Chronological

I’ve searched a lot on this issue and I found some earlier threads on this but the bug in earlier versions (2.7) regarding incorrect comment order is marked as closed and the other threads seem to relate to threading.

Anyway the problem I’m having is comments are showing up in random places.

For example this comment:

http://www.thenutgraph.com/fear-of-the-cross/#comment-19984

Which is from August 11th but is showing up before July 27th.

The comment is not in reply to anything and I even checked the database, the comment is listed with a comment_parent value of 0.

mysql> select comment_parent from wp_comments where comment_ID =’19984′;

+—————-+
| comment_parent |
+—————-+
| 0 |
+—————-+

I’ve also switched to the default theme (twenty-ten) and it’s exactly the same so it’s not a theme issue.

This issue is occurring quite a lot and many users are complaining their comments are not showing up in order.

Any ideas on how I can go about finding the problem, and of course rectifying it.