Is this server error or script error?

I check and all the files are there. sometimes it works sometimes it doesn't

Warning: require_once(BxDolConfig.php) [function.require-once]: failed to open stream: No such file or directory in /home/crispe/public_html/inc/classes/BxDolFilesConfig.php on line 22

Fatal error: require_once() [function.require]: Failed opening required 'BxDolConfig.php' (include_path='') in /home/crispe/public_html/inc/classes/BxDolFilesConfig.php on line 22

It is not a script error.  The server could not find the file BxDolConfig.php.  Why it can sometimes find it and sometimes it can't I am not sure.

Thank you, start moving host now.