Fatal error "function require"

My site has completely crashed (and, no, I haven’t changed anything since it last worked) at the URL I get;
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Warning: require(/home/content/n/y/c/nycticorax/html/wp-includes/version.php) [function.require]: failed to open stream: No such file or directory in /home/content/n/y/c/nycticorax/html/wp-settings.php on line 30

Fatal error: require() [function.require]: Failed opening required ‘/home/content/n/y/c/nycticorax/html/wp-includes/version.php’ (include_path=’.:/usr/local/php5/lib/php’) in /home/content/n/y/c/nycticorax/html/wp-settings.php on line 30
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I can’t even log in (or check to see what version I’m running) Haven’t got a clue what’s going on; can anybody help?
Thanks -Fr Joseph Valentine