Visual Studio 2012 Extension Issues

The other week I ran an update through the extension manager to update a particular extension. When I restarted Visual Studio I was greeted with an error saying to check the ActivityLog.xml file. Looking in that file I saw it was trying to load an extension that didn't exist any more, so I removed it from the registry using the GUID as a reference.

It seems thought I am still getting oddities with extensions. Whenever I install a new extension the ActivityLog shows it has been loaded without error yet they never show in Visual Studio. At one point I even had an old extension menu option in Tools -> Options that simply gave an exception when clicking it.

I am also getting errors when opening a solution file, like so:

I have tried to repair and reinstall Visual Studio 2012, but to no eval. Has anyone else encountered this?

Edit It appears that when I got another user to sign onto my machine and open Visual Studio for the first time it all worked for him. He was able to install extensions and see them instantly, so maybe something in my user profile is corrupted - any ideas on this?

I am going to post this as an answer, but I cannot confirm 100% that this is the correct solution...

I closed down all instances of Visual Studio 2012.
Deleted the C:\Users\toha\AppData\Local\Microsoft\VisualStudio\11.0 and C:\Users\toha\AppData\Roaming\Microsoft\VisualStudio\11.0 folders.
Opened regedit.exe and deleted the HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\11.0 and HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\11.0_Config keys.
Restarted my PC before opening Visual Studio 2012.
Started Visual Studio 2012 and went through initial setup and it just...worked.

I am sure I tried doing these steps when I posted this question, but I may not have restarted my computer. Either way, like I said, not too sure if it's a solution, but it's what seemed to work for me.

Edit: The issue persisted and one solution that is working for me currently is this:

Get another user to log onto the computer.
Once logged in open Visual Studio 2012.
Open regedit.exe and export the HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\11.0_Config key.
Save the export somewhere like C:\temp.
Log back into your user and close all instances of Visual Studio 2012.
Open regedit.exe and delete the HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\11.0 and HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\11.0_Config keys.
Import the earlier exported HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\11.0_Config key.
Restart Visual Studio 2012.