Admin's not working anymore (but the catalog is)

[rotoxtc]

When I try to open the admin page, i get this error message:

 

 

Warning: main(includes/configure.php): failed to open stream: No such file or directory in /home/***/www/catalog/admin/includes/application_top.php on line 29

 

Fatal error: main(): Failed opening required 'includes/configure.php' (include_path='.:/usr/share/php:/usr/share/pear') in /home/***/www/catalog/admin/includes/application_top.php on line 29

 

Everything was working fine until this morning, and I didn't change anything. I noticed the server had some problems earlier (it was very slow, or I couldn't connect at all), and now the catalog is still working, even if sometimes it's very slow.

 

Any ideas?

 

Thanks