If the other answers aren't working for you, try this instead. It removes all ignores for the form, so it would validate everything including hidden fields:
$.data($('form')[0], 'validator').settings.ignore = "";
To restore the settings to ignore hidden fields, use something like this:
$.data($('form')[0], 'validator').settings.ignore = "input[type='text']:hidden";
You can also use the above code to read back the current value.