about error message, I'd suggest a modification I'm using in forms.elm :
<inp2:m_DefineElement name="inp_edit_box" style="" maxlength="" no_editing="1" is_last="0" title="">
<tr class="<inp2:m_odd_even odd="table_color1" even="table_color2"/>" <inp2:m_if check="{$prefix}_HasError" field="$field">style="background-color:#FFE5E6"</inp2:m_if>>
...
this way the line in error have a -nice- light red background, showing very easily where does the error come from.