Code Window does not highlight selected (usually .cs) file in "Solution Explorer"

Question

My Visual Studio has done something really weird.

Usually, when you are in the "edit window" and are changing code, the file you are editing will highlight in "Solution Explorer".

Also, if all projects are "collapsed" in "Solution Explorer", and then there is a file already open (as in, you can see its "tab"), when you click the tab of that file (to be able to edit it), the Solution-Explorer will un-collaspse that project and highlight the file you are editing.

My "Solution-Explorer-Highlight-The-Current-File" function has stopped working.

I can move from tab to tab to tab, and Solution-Explorer doesn't react at all.

I've googled and binged, and I either get 5 billions hits ... or none. The key phrases are too ambiguous I think.

Anybody ever seen this one?

I have VS2010 on the same machine, and it works just fine.

I have one Add-In installed, but it is installed in both VS2010 and VS2012. Thus I don't think it's the culprit.

Answer 1

Smaller hammer.

From the menu: Tools -> Options

From the tree: Projects and Solutions -> General

On the form check: Track Active Item in Solution Explorer

Answer 2

Well.

From here:

How do I truly reset every setting in Visual Studio 2012?

I found this "Big Hammer" command line switch.

/ResetUserData

I used it.

And now it works.

I hate to answer something myself, but just in case somebody hits this in the future.