After upgrade to 2.7 the wp-admin is gone

I upgraded to 2.7 and a strange thing happened – if I try to access the /wp-admin URL on my website it shows the “Nothing found” error. But the wp-admin folder is physically there, with all the files in it, I can see it on the FTP. Besides that, the site runs OK, only the admin section is not accessible.

Any ideas? Thanks in advance!