I set up a wordpress blog for a friend a couple of years back. He used the one click upgrade recently and since then when he tried to log in he gets:
ERROR: Cookies are blocked or not supported by your browser. You must enable cookies to use WordPress.
If I go to /wp-admin all I see is a blank page, no login box, though I’ve checked the index.php and it all seems complete. I can go to /login.php and attempt to login but I get the cookies message. Have tried 3 browsers, clearing caches, cookies most definitely turned on.
Thinking he screwed up the install, I did a manual reinstall but this hasn’t helped.
your theme have problem,
go to your file manager public_html/wp-content/themes and change name of your theme folder ex : shandiz => shandiz1 , after you can login to wp-admin and choose another theme or fix old theme.