add-site function fails

Hi All

I am having an issue creating a new site. When I try and create a new site, the databases tables are created but the folder is not created, and I get a 404 error when I try and access it.

I need to find the add-site function from the form below so I can debug this issue?

Can anyone help with this?

<form method="post" action="<?php echo network_admin_url('site-new.php?action=add-site'); ?>">
<?php wp_nonce_field( 'add-blog', '_wpnonce_add-blog' ) ?>
	<table class="form-table">
		<tr class="form-field form-required">
			<th scope="row"><?php _e( 'Site Address' ) ?></th>
			<td>
			<?php if ( is_subdomain_install() ) { ?>
				<input name="blog[domain]" type="text" class="regular-text" title="<?php esc_attr_e( 'Domain' ) ?>"/>.<?php echo preg_replace( '|^www\.|', '', $current_site->domain );?>
			<?php } else {
				echo $current_site->domain . $current_site->path ?><input name="blog[domain]" class="regular-text" type="text" title="<?php esc_attr_e( 'Domain' ) ?>"/>
			<?php }
			echo '<p>' . __( 'Only the characters a-z and 0-9 recommended.' ) . '</p>';
			?>
			</td>
		</tr>
		<tr class="form-field form-required">
			<th scope="row"><?php _e( 'Site Title' ) ?></th>
			<td><input name="blog[title]" type="text" class="regular-text" title="<?php esc_attr_e( 'Title' ) ?>"/></td>
		</tr>
		<tr class="form-field form-required">
			<th scope="row"><?php _e( 'Admin Email' ) ?></th>
			<td><input name="blog[email]" type="text" class="regular-text" title="<?php esc_attr_e( 'Email' ) ?>"/></td>
		</tr>
		<tr class="form-field">
			<td colspan="2"><?php _e( 'A new user will be created if the above email address is not in the database.' ) ?><?php _e( 'The username and password will be mailed to this email address.' ) ?></td>
		</tr>
	</table>
	<?php submit_button( __('Add Site'), 'primary', 'add-site' ); ?>
	</form>