None of the solutions I found around, including those listed here, seemed to help. What did work was going in the software install/uninstall management, right clicking on Visual Studio and choosing "change" (that's where you would normally uninstall something from).
That should pop up the Visual Studio package manager, and from there you can choose repair.
In my case, looking at the systems backlog and restore points, it seems it was one of the Visual C++ redistributables, possibly installed by some game, that compromised the environment.
This is on Windows 8.