SOLVED Cannot login - redirects back to login page - no errors

[JAKE]

And still have this problem.

Now I can say that it is related to Firefox since within Chrome I can login and use admin as usually.

What could be so different in Firefox?
First I access login page /gs/cms/ and after submit I get redirected to/gs/cms/index.php?redirect=pages.php?

EDIT: And this is a new site.