Magento connect manager redirects to homepage

I have also facing the issue of when I click on Magento Connect Manager it redirects to the homepage of my site.

Downloaded magento and reinstalled downloader to my store root directory 
- Deleted my var/cache and var/sessions
- Deleted connect.cfg and cache.cfg from downloader folder

Refresh site and again connect magento connect manager.

If your problem solve please comment me.

thanks