When you work with Turnkey you are advised to always run the latest MDriven Designer.
The latest MDriven Designer is always available via this link MDriven Designer
The link is a ClickOnce application installer – that will refresh MDriven Designer to the latest version before starting.
ClickOnce works natively in Internet Explorer but requires a plugin for Chrome and for Firefox.
Windows sometimes get confused by which ClickOnce application has been cached and gives an error.
To clear the cache, start an command prompt with administrator privileges and execute
rundll32 dfshim CleanOnlineAppCache