Phrase and relative position Error Message

It appears that the "phrase" captcha returns an error message each time even when correct. When correct it does allow for the comment to be saved (as though there was no error.) Likewise real errors stop the comment from being saved. This is highly confusing to the user. Same problem with the "unrelated word" captcha. The specific error message in both cases is "An illegal choice has been detected. Please contact the site administrator." Thanks for your attention in this matter.