Functions Error

For a while now I’ve been getting this error when updating plugins, installing something new, going to my dashboard, other random stuff:

Warning: fopen(C:\Inetpub\vhosts\therichstyle.com\httpdocs/wp-content/themes/Brunelleschi2/style.css) [function.fopen]: failed to open stream: Permission denied in C:\Inetpub\vhosts\therichstyle.com\httpdocs\wp-includes\functions.php on line 4339

Warning: fread(): supplied argument is not a valid stream resource in C:\Inetpub\vhosts\therichstyle.com\httpdocs\wp-includes\functions.php on line 4342

Warning: fclose(): supplied argument is not a valid stream resource in C:\Inetpub\vhosts\therichstyle.com\httpdocs\wp-includes\functions.php on line 4345

I recently finally made a child theme but only have the stylesheet in there. I don’t have a clue as to what is going on and really need some help.

Here’s my site: therichstyle.com
And I’m using the latest update of the Brunelleschi theme.

I also can’t update to the latest version of WordPress because of this error. Additionally, I can’t backup my site before I update WordPress because of these errors. I tried numerous backup plugins to no avail.

Help!