Make sure windows is still fully updated until 'No New Important Updates are Found' (this may require multiple restarts and multiple 'check for updates'), including Internet Explorer (even if you use a different web browser).

Reinstall Microsoft .NET Framework:

If Vista/XP:
1) Download, unzip and run the latest version of the .Net Framework Cleanup Tool from the bottom of this page.
2) Install 3.5 SP1 from here.
3) Then install 4.0 from here.


If Windows 7:
1) Download, unzip and run the latest version of the .Net Framework Cleanup Tool from the bottom of this page.
2) Install 4.0 from here.
3) Install 4.5.2 from here.


If Windows 8/10:
1) Download, unzip and run the latest version of the .Net Framework Cleanup Tool from the bottom of this page.
2) Install 4.5.2 from here.