Need help! Can't acces my site admin

Hi,

everytime I login I will get this message:

“Warning: require_once(./admin-header.php) [function.require-once]: failed to open stream: No such file or directory in /home/xxxx/public_html/xxxxxx/wp-admin/index.php on line 45

Fatal error: require_once() [function.require]: Failed opening required ‘./admin-header.php’ (include_path=’.:/usr/lib/php:/usr/local/lib/php’) in /home/xxxxx/public_html/xxxxx/wp-admin/index.php on line 45″

I just move to new hosting while I don’t have any file on my old hosting.

Right now, I just have the .xml file that I export before I move to new hosting.

Anyone can help me?

Thanks