Magento 1.9 Can’t login to admin panel!

Question

I have installed Magento 1.9. It was working well for a week. Suddenly yesterday, when I tried to login to the Magento admin panel and I typed username and password, clicked Login button and nothing happened. The page refreshes and that’s all. No error or any other messages.

If I entered wrong username or password, It shows error.

After I googled about this issue, I was recommended to comment following lines in:

app\code\core\Mage\Core\Model\Session\Abstract\Varien.php

/* to solve login issue */
  /*if (!$cookieParams['httponly']) {
  unset($cookieParams['httponly']);
  if (!$cookieParams['secure']) {
  unset($cookieParams['secure']);
  if (!$cookieParams['domain']) {
  unset($cookieParams['domain']);
  }
  }
  }

if (isset($cookieParams['domain'])) {
  $cookieParams['domain'] = $cookie->getDomain();*/ //I have commented these lines

And for some older versions below was recommented in the same file.

$cookieParams = array(           
    'lifetime' => $cookie->getLifetime(),           
    'path'     => $cookie->getPath(),           
    //'domain'   => $cookie->getConfigDomain()           
    //'secure'   => $cookie->isSecure(),           
    //'httponly' => $cookie->getHttponly()       
);
  }*/

Even after that, I could not login into admin. It is as it was. Anyone faced this issue? Is there any other solution to this issue?

(I tried clearing cache and session through ftp).