Hi,
depending on what server configuration your new provider is using it might be needed to change authentication setting. Please check your confic.inc.php file and look for line containing:
@define('AUTH_METHOD', 'basic');
try changing the value to 'basic', 'digest' or 'none' - one of them should work (where 'none' is no security). In any case, you should address any further question to your new provider, as we can't really help you with that.
good luck!