This works, but a bit hackish.... I first set all the vars to true and then they get changed to false as the user fills out the form. I tried the array thing, but couldn't get it to work out.

Code:
function checkForm(form){
        if (usernameerror || pworderror || emailerror || firstnameerror || lastnameerror){
          document.getElementById('form_help').innerHTML = '<img src="images/info.jpg" alt="" width="25" height="24" />&nbsp;&nbsp;Please correct any errors and re-submit.';
        return false;
         } else {
          return true;
         }
}