ITunes search displays results but isn't clickable?

Question

When I click on the search bar to search through my library, it displays a drop down of results, but they aren't clickable. I used to be able to click on results (for example an artist or album) and it would take me straight to that result in my library. One day it just stopped working and I'm not sure why.
If I uncheck the "search entire library" option, it filters my results on the left bar, but doesn't display the results in a drop down anymore, which I liked. If I'm in the "playlists" pane and search for an artist that's not on my current playlist, it just hides all the songs in my current playlist.
I am using iTunes 11.1.2.32 on Windows 7, but this issue has been persistent through the past couple updates of iTunes (not entirely sure when it started, but definitely in iTunes 11)

Answer 1

The behavior of the search dropdown has changed (can't recall whether it was iTunes 11 or 12), but the functionality you refer to is still available ... sort of.  With the Search Entire Library function enabled, when you enter a search string it'll show the matching results:
In this case I searched for "hotten" and got four matching songs.  Clicking on the highlighted bar will show all the matching results in the current view prior to the search - so in this case if I started from Albums view it'll show the three albums that include matches:
If I start from Songs view (or switch to Songs from the filtered view above) I get:
Other functions are available by hovering over (not clicking) on the songs shown in the dropdown.  When you do this a "+" appears to the left of the song and an ellipsis ("...") to the right.  Then, clicking on the "+" adds the song to the Up Next list.  Clicking on the ellipsis opens a submenu with other options:
However, as you rightly point out, this functionality is not available when the Search Entire Library option is disabled.  The bizarre thing here is that when you are viewing a playlist and have Search Entire Library option enabled you get mixed results - the dropdown shows all the matches in your library (whether in the playlist or not), but the top line of the dropdown now says "Show <search name> in <playlist>" and will take you just the matches in the current playlist ... mightily confusing .
Right now this is probably classified as a "feature", i.e., the omission of the extra options when Search Entire Library option is not selected may be intentional on Apple's part (though who knows why that should be) or could equally well be the result of a bug.  May be worth reporting this at https://www.apple.com/feedback/itunesapp.html.
BTW, atra1n's suggested solution looks highly dubious.  First. hacking at the registry rarely has the desired effects (or produces unforeseen side effects). Secondly, the registry keys under HKEY_CURRENT_USER\Software\Apple Computer, Inc.\iTunes are related to (or appear to be related to) Outlook integration, Parental Controls, and automatic iDevice syncing - nothing related to search functions.