New flush() for APC object Cache - accounts for multiple sites on using one cache.

object-cache-flush.php

function flush() {
	// Don't flush if multi-blog.
	if ( function_exists( 'is_site_admin' ) || defined( 'CUSTOM_USER_TABLE' ) && defined( 'CUSTOM_USER_META_TABLE' ) )
		return true;

	$user_cache = apc_cache_info( 'user' );

	foreach( $user_cache['cache_list'] as $cache_entry ) {
		if ( false !== strstr( $cache_entry['info'], WP_APC_KEY_SALT . ':' . $this->abspath ) )
			apc_delete( $cache_entry['info'] );
	}
	return true;

	// return apc_clear_cache( 'user' );
}