What? Good question.
In the middle of working I thought I'd add a new class to my project when low and behold I get a dialog box:
No Visual Studio template information found. Seel the application log in Event Viewer for more details.
Ok, so I open up event viewer and find this
Event Type: Warning
Event Source: Visual Studio - VsTemplate
Event Category: None
Event ID: 1
Time: 4:31:56 PM
The Visual Studio template information is out of date. Regenerate the templates by running 'devenv /installvstemplates' or reinstalling Visual Studio. Note: corrective action requires Administrator privileges.
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
Except a lot of them. I have no idea why this suddenly started happening. Well let's check google
Sigh....I'll probably just run the command line as it seems to fix it. Hopefully it doesn't break ViEmu or R# or TD.Net.