Error messages when trying to comment

Hey,

No body (apart from myself!) is able to leave messages on the blogs on our site. I logged out and it let me do it, but yesterday, everyone else got a “enter valid email” message, even though they had. I changed the settings, so that an email was not required, then got someone to check for me. First they could not find where to comment at all, then all they got was an “error” message.
Would really appreciate some help! My husband is the computer whiz in our house, but he is about to deploy (military). Me on the hand, know very little about computers and have no clue how to put this right!