wp_safe_redirect

Hi

I installed 2.3 a few weeks ago, and everything went ok, but since a couple of days, I suddenly got the following problem

Everytime I go to wp-login.php and log in, I get the following error:
Fatal error: Call to undefined function wp_safe_redirect() in /home/xxx/domains/xxxx.com/public_html/wp-login.php on line 328

and it logs me in, because if I go to wp-admin, I’m logged. Once there, if I logout, I get the same error but on line 82. Those two lines are just:

wp_safe_redirect

Any ideas?

Thanks in advance