I have experience on getting an error after install Visual Studio 2012 on a new Win7 professional machine.
'Microsoft.VisualStudio.Editor.Implementation.EditorPackage' package did not load correctly
After getting some searching and found out that the solution is pretty simple. Removing %LOCALAPPDATA%\Microsoft\VisualStudio\11.0\ComponentModelCache and restarting VS2012 fixed the problem for me. Hope this will help if you meet the same error.