“Save” button in sidebar does not work – non stop “saving”

Hello
I had a wp blog running and today I have changed it to another domain. I have reinstalled wp and import the pages and posts of the other blog. Now I have a problem: my 5 sidebars (I created 4 for the other blog) are empty, and when I try to put widgets on them (tags, text…) the “save” button does not work. Inmediately after putting the widget in the sidebar, the button starts “saving” and it does not stop. And it does not save anything.

I have to say this morning I had another problem with importing and i changed the following code at wp-admin/admin-header.php:
“if ( ! defined( ‘WP_ADMIN’ ) )”
“require_once( ‘./admin.php’ ); “

instead of:
“if (!isset($_GET[“page”])) require_once(‘./admin.php’);”

I changed it because I saw it in https://core.trac.www.ads-software.com/changeset/14334, and it worked. I only write this just in case you think it may be a relation between the 2 problems. Anyway, i tried changing that code again and the thing with “save” button does not work either.

Thank you very much for reading and very very very much if you have a solution ??

Maialen