Login/Logoff/Create Acccount etc goes to Blank page

Hi
I am getting a strange problem
Whenever I login, I get redirected to a blank page with the browser url as

http://www.mysite.com/index.php?main_page=login&action=process

When I click Refresh, nothing happens(same blank page)
But when I click on Back in browser, I see the 'My Account', 'Log Off' etc links indicating that I have logged in the site
Same is the case with 'Log Off' and Create Account
Can someone tell me whats happening
I tried to debug the file
/public_html/includes/modules/pages/login/header_php.php
and came to know that the problem is here
zen_redirect(zen_href_link(FILENAME_DEFAULT, '', $request_type));
Also, tried using

zen_redirect("www.google.com") 
//or
header('Location: ' . 'www.google.com'); 

for testing but nothing seems to work

Can someone please help me?
I already went through this link
https://www.zen-cart.com/tutorials/index.php?article=82

Got it
the problem with spaces in /public_html/includes/modules/pages/login/header_php.php

I"m having this problem as well.

this....
http://www.duosandtrios.com/shop/index.php?main_page=login

goes to an empty page. I don't understand how you all fixed this. Can someone explain to me what's going on here?

Thank you

Look here:

https://www.zen-cart.com/tutorials/index.php?article=82

Most 'blank page' problems are caused by corrupted files or files that have been improperly edited, often in WYSIWYG editors.

I have the same problem, but I just figured out why!!! When I click on the customer login page, the browser looks for https://blahblah instead of http://blahblah. Sooo, I'm hoping that once I get my ssl certificates setup, everything will be hunky dory! Wish me luck!