ClickOnce：此计算机上未安装所需的.NET Framework版本

I have been getting the error "The required version of the .NET Framework is not installed on this computer." (Event Id 4096 in Event log) when trying to install a VSTO application from both a ClickOnce deployment and a local copy. This is interesting as the .NET framework is installed (on my 32bit Windows 7 PC) and the VSTO application was developed on the self same machine (and works in Visual Studio 2008).I have been getting the error "The required ver