i think the problem is because you are using the form as a plugin.
try changing the form tag:
<form class="Sharp_Default" id="SimpleContact_Sharp_Default" name="SimpleContact_Sharp_Default" method="post" action="../Contact">
to:
<form class="Sharp_Default" id="SimpleContact_Sharp_Default" name="SimpleContact_Sharp_Default" method="post" action="<?php echo(htmlentities($_SERVER["PHP_SELF"], ENT_QUOTES)."?".$_SERVER["QUERY_STRING"]); ?>">