Some older versions of internet browsers such as Internet Explorer have strict security settings that can prevent you from editing your site even after you have logged in. If you are unable to make edits to your site after you have logged in, it may be due to the security settings on your computer.
A quick change in settings will resolve it:
From Internet Explorer
Go Tools > Internet Options
Click the "Privacy" tab
Click "Sites" and put in the domain name ( websitedomainname.com ) in the box and click "Allow".
Try logging in again and you should be fine.