Channel Ratings "Unable to receive your comment at this time." Error

Question

I'm getting this very unhelpful message when I try to submit a review form:

The form you submitted contained the following errors

Unable to receive your comment at this time.

This error doesn't give me much to go on, so I don't know where to start debugging it. Here's my template code:

{exp:comment:form 
  channel='products' 
  entry_id='{structure:page:entry_id}' 
  parse='inward' 
  form_class='member-review' 
  rating:enabled='yes' 
  rating:required='yes' 
  rating:collection='member_reviews' 
  rating:min_value='1' 
  rating:max_value='5' 
  rating:return='notifications/submission-success/product-review'
}
  {if rating:not_rated}
    <div class="alert-box ajax-form"><a href="#" class="close">&times;</a></div><!--.alert-box-->
  {/if}

  <div class="form-body">
    {if rating:already_rated}
      <p class="already-rated">You have already rated this product.</p>
    {/if}

    {if rating:not_rated}
      <div class="sub-ratings">
        <div class="rating-field">
          <div class="rating-name">
            <label for="rating-directions">Directions:</label>
          </div><!--/.rating-name-->
          <div class="rating-input">
            <input type="radio" name="rating[directions]" value="1" checked="checked" class="star required">
            <input type="radio" name="rating[directions]" value="2" class="star">
            <input type="radio" name="rating[directions]" value="3" class="star">
            <input type="radio" name="rating[directions]" value="4" class="star">
            <input type="radio" name="rating[directions]" value="5" class="star">
          </div><!--/.rating-input-->
        </div><!--/.rating-field-->

        <div class="rating-field">
          <div class="rating-name">
            <label for="rating-packaging">Packaging:</label>
          </div><!--/.rating-name-->
          <div class="rating-input">
            <input type="radio" name="rating[packaging]" value="1" checked="checked" class="star required">
            <input type="radio" name="rating[packaging]" value="2" class="star">
            <input type="radio" name="rating[packaging]" value="3" class="star">
            <input type="radio" name="rating[packaging]" value="4" class="star">
            <input type="radio" name="rating[packaging]" value="5" class="star">
          </div><!--/.rating-input-->
        </div><!--/.rating-field-->

        <div class="rating-field">
          <div class="rating-name">
            <label for="rating-overall">Overall Satisfaction:</label>
          </div><!--/.rating-name-->
          <div class="rating-input">
            <input type="radio" name="rating[overall]" value="1" checked="checked" class="star required">
            <input type="radio" name="rating[overall]" value="2" class="star">
            <input type="radio" name="rating[overall]" value="3" class="star">
            <input type="radio" name="rating[overall]" value="4" class="star">
            <input type="radio" name="rating[overall]" value="5" class="star">
          </div><!--/.rating-input-->
        </div><!--/.rating-field-->
      </div><!--/.sub-ratings-->

      <div class="fieldgroup comment">
        <label for="comment">Share your review with others</label>
        <textarea name="comment" id="comment" rows="8" class="required"></textarea>
      </div><!--/.fieldgroup-->

      <div class="submit-wrap">
        <input type="submit" value="Comment">
      </div><!--/.submit-wrap-->
    {/if}
  </div><!--/.form-body-->
{/exp:comment:form}

Answer 1

This error is coming from EE core, not Channel Ratings. It happens when a duplicate comment is submitted (like a test comment, i.e. "test"). Source.