Hi there,
I have the same problem. Editing the the class-pixelentity-theme-update.php file did’t solve it. I get the same error as jeroenvandessel. the given url is not right. The current version is 3.6.1 and I wish to update to the latest version.
When I updated through FTP, I had a blank page and couldn’t get to wp-admin (also blank page). Do you have a solution?

Thanks in advance,
Dineke