After some analysis, and retrying on other browsers, i decided that the cookies(from google.com.*) that are saved by Maxthon browser, are corrupted.
As, Maxthon has no user-friendly option to clear cookies only, I had to work under the hood for work around.
- Open the login page
- Open Developer tools. Main_Menu --> Tools --> Developer's tool.
- Click "Resources" tab, navigate to "Cookies" section, select Google.*
- Delete each of the line individually
- Reload the page with "CTRL+F5", not just F5.
Now the page loads with no "preloaded" email address. Now, i could sign-in easily.