Basically, I've been working on a program for quite some time without issues. I came upon this issue when adding another window/form. It happened for a bit, so I reinstalled Visual Studio. It went away for a bit. Now, it's back and stopping me from using the Designer on anything. I can only write code, which is seriously hampering everything I do (obviously). I decided to Debug it and see what the Exception was, and I get this lovely piece of work:

Code:
System.ArgumentNullException was unhandled
  Message=Value cannot be null.
Parameter name: sp
  Source=Microsoft.VisualStudio.Shell.10.0
  ParamName=sp
  StackTrace:
       at Microsoft.VisualStudio.Shell.ServiceProvider..ctor(IServiceProvider sp, Boolean defaultServices)
       at MS.Internal.Package.Toolbox.AutoToolboxProjectManager.get_VSProject()
       at MS.Internal.Package.Toolbox.AutoToolboxProjectManager..ctor(IVsHierarchy hierarchy, IServiceProvider provider, IVsSmartOpenScope smartOpenScope)
       at MS.Internal.Package.Toolbox.AutoToolboxManagerService.Update(IVsHierarchy hierarchy, Boolean force)
       at MS.Internal.Package.Toolbox.AutoToolboxManagerService.Start()
       at MS.Internal.Package.DesignerPackage.<>c__DisplayClass2.<Initialize>b__0(Object arg)
       at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
       at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)
       at System.Windows.Threading.DispatcherOperation.InvokeImpl()
       at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(Object state)
       at System.Threading.ExecutionContext.runTryCode(Object userData)
       at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData)
       at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Windows.Threading.DispatcherOperation.Invoke()
       at System.Windows.Threading.Dispatcher.ProcessQueue()
       at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
       at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
       at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
       at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
       at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)
       at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
       at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
  InnerException:
It is a vanilla installation of Visual Studio, and I am just trying to use the Designer. I think it happens as it's trying to load the Tool bar, but I could be wrong.