Thanks for detailing what steps you have performed already. When it comes to renaming or deleting your configuration folder you should do this then open the extension manager to remove any extensions that are listed there. After you remove them all then you can try installing the Validation Toolkit again to see if the problem persists. Also make sure that you visit your download history and obtain the latest release for your extensions. Let us know if you have done this or if you get the same result after doing this and we can look into this further with you.
