Cannot post comments – Please help

I am having an issue with one of my clients site. When a user tries to submit a comment it takes them to a blank /wp-comments-post.php page. It does not redirect them like usual or submit the comment.

This did not occur before installing Custom Anti-Spam Image plugin. I have removed the plugin and no luck. I’ve even upgraded to 2.1.2 and no luck.

So. I went into my phpmyadmin and what you know there is an error. Error stats the following: “More than one INDEX key was created for column comment_post_ID” So I have the normal ‘column_post_ID’ key and also a ‘column_post_ID_2’ key.

Could someone tell me if this is the reason why users are not being able to post comments?

and also: what should I do with ‘column_post_ID_2?’

any help would be appreciated. and if you need more info from me, please ask.