Fatal Error - happens occasionally?

Warning: Unknown: failed to open stream: Permission denied in Unknown on line 0

Fatal error: Unknown: Failed opening required 'J:/xampp/htdocs/mylocalhostname/register.php' (include_path='.;\xampp\php\PEAR') in Unknown on line 0

I am getting the above error, only occasionally, as one of my pages loads, I am not sure what it means.

Is it refering the the path / url of my includes files in that page? This is how I include a file within that page:

$Incfile = 'includes/createphotot.inc.php';

if (file_exists($Incfile) && is_readable($Incfile)) {

include($Incfile);

}

Am I linking to my includes file correctly or maybe it should be a full URL?

It is very strange that the error only seems to occur 10% on the time so I haven't yet established under what circumstances it is occuring.

Any help would be very much appreciated.

Thank you