Unable to login to WordPress admin area. No Errors shown.

I had recently updated the latest version of WordPress 3.3.1. and also added a couple of plugins. The blog was running smoothly for a week. It was yesterday when I found myself unable to login to the admin area. It doesn’t show any error message instead it lands back on the wp-admin page.

I have tried resetting password and disabling the plugin through PhpMyadmin but all in vain.

How can I fix this thing?