I had the same kind of problems and for me it was solved by including a line in the config.inc.php file that appears to be missing... see also [
forum.wampserver.com]
So check whether the line:
$cfg['Servers'][$i]['AllowNoPasswordRoot'] = true;
exists in the file named "config.inc.php" located in C:\wamp\apps\phpmyadmin3.1.1.