WordPress MU

We installed WPMU, 2.7 and have it running nicely but whenever we have a user post comments, no matter what blog, or if the user is logged in or out, when you submit a comment and hit "submit" the comment is posted TWICE to the blog.

We then receive the following error:
"Duplicate comment detected; it looks as though you've already said that!"

/wp-comments-post.php

if you then go back and refresh the blog, the original comment appears.

Why is this posting twice??? I cannot find anything searching this issue yet.

TIA,
Tony

Try different themes? Disable all plugins and test?

I found the problem, thanks for your help.

Could you share how this was resolved? I'm coming across the same issue.