I just set up a new WP blog, everything going sweet, put out the first post and asked for comments...I even tested by making the first comment and deleting it. Now no one can comment, I didn't change very much, but I've been up and down changing settings and disabling plug-ins and all I can say is have you seen this before and any idea what to try?
Mine had the same problem and I had missing code in the single.php file. Look in the default template that came with your blog and specifically look in single.php and compare the two. Copy the missing code from the default file to the new template file and see if that works. Also make a backup first though. Because I had my template specially created for me, some code and pages were left out. For example, I was also missing the comments.php file and comments-popup.php file in my cpanel. You might want to check that as well.