Hi Samadaslam.,
May i know your installed plugins list
If this was caused by bugs in WP 3.6.1, a lot of people will be complaining about the same thing as you, so you need to find out what it is about your instance that has a problem.
Temporarily deactivate all plugins and switch to the default theme. If this helps, reactivate the theme & plugins one-by-one to identify which one has a problem.
If the above does not help, ensure that you have all of the WordPress files. Download & extract the installation zip and upload the files manually – see http://codex.wordpress.org/Updating_WordPress#Manual_Update
Unable to do anything. It’s not going anywhere now. Not even on plugin tab. I reinstalled wordpress but problem is same.
Is it the same using a different browser?
If you cannot deactivate plugins in admin, you can use ftp to temporarily rename the plugins directory in wp-content to ‘plugins-hold’, visit the plugins page in admin to see they’re not active then change the directory name back to plugins.
How did you reinstall? was it a manual update or one-click?
I checked in all browsers. Now i deleted that subdomain. Deleted directory and recreated all again and installed wordpress. Again the same problem. Unable to understand it.
No plugin installed except which comes by default. like holly dolly and askimet
What is the URL of the site?
What theme are you using?
Is it the same if you use the default twentythirteen theme?