Try showing the search form with get_search_form(): http://codex.wordpress.org/Function_Reference/get_search_form
Or try naming the name attribute "s".
<form method="get" id="searchform" action="<?php echo home_url( '/' ); ?>">
<div>
<input class="text" name="s" size="32" maxlength="64" />
</div>
</form>