Login loop problem after update WP to 2.6.2

Today I updated my blog (to from version 2.6 to version 2.6.2. I was ok to enter in my blog admin area, but now I can’t. It accepts the password (and gives login error message when not the right password).
It accepts the password and then keeps on logging in but never shows dashboard page. I am unable to update my blog.
I have clean browser cache, I tested with Firefox, IE and Safari, I updated to the new version (while I was able to login) via automatic update and then manually (by following the manual update tutorial) after the login problem occurred.
I have requested a new password but with no results.
I think the database is ok (once it knows when the password is wrong and the blog is ok). So I thin it is a problem after the login that sends me back to the login page.
When I did the manual update,I set the three custom secret keys (cookie security measures) in wp-config.php. Before (in the previous version) I had just one!