PHP Warning with new 4.0 update

Hey,

So I am encountering an error now that I have updated my wordpress core to 4.0 (or more specifically, the fact that I have tried to update).

I do not know if this is something to do with the theme, or anything you can help with, but I’m posting here just in case it is.

When I click on the ‘update wordpress’ button, it starts loading and then I get the following error:

PHP Warning: copy(G:/PleskVhosts/escort-erotica.com/spacestationapes/wp-admin/includes/update-core.php): failed to open stream: Permission denied in G:\PleskVhosts\escort-erotica.com\spacestationapes\wp-admin\includes\class-wp-filesystem-direct.php on line 217

I have spoken to my hosts, but they say there’s nothing they can do on their end. The permissions seem to be set right for the file in question.

Line 217 is:

$rtval = copy($source, $destination);

Which is part of the following code:

function copy($source, $destination, $overwrite = false, $mode = false) {
		if ( ! $overwrite && $this->exists($destination) )
			return false;

		$rtval = copy($source, $destination);
		if ( $mode )
			$this->chmod($destination, $mode);
		return $rtval;
	}

Any advice on this matter would be gratefully received.

Thanks ??