Microsoft Visual Studio XAML UI Designer has stopped working

Edit: SOLVED! SCROLL TO BOTTOM!

I'm getting the following error when trying to view the XAML Designer in VS2012:

I noticed this problem when working on a existing project, however I also get this error when I create a brand new WPF project. The top of the stack trace is for theNEW project is:

 Microsoft.Expression.DesignHost.Isolation.Remoting.RemoteException
Object reference not set to an instance of an object.
   at Microsoft.Expression.DesignSurface.View.SceneView.TextEditor_CaretPositionChanged(Object sender, EventArgs e)
   at Microsoft.Expression.DesignSurface.TextEditorContext.CaretPositionChangedPipe(Object sender, EventArgs args)
   at ...

However, the stack trace for the EXISTING project is different:

   System.IO.IOException
The file exists.

   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.IO.__Error.WinIOError()
   at System.IO.Path.InternalGetTempFileName(Boolean checkHost)
   at System.Windows.Input.Cursor.LoadFromStream(Stream cursorStream)
   at System.Windows.Input.Cursor..ctor(Stream cursorStream)
   at Microsoft.Expression.Utility.FileResourceManager.GetCursor(String name)
   at ...

I also get the following message:

Checking the given file in the error message here is what I get:

System.IO.IOException: The file exists. at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath) at System.IO.__Error.WinIOError() at System.IO.Path.InternalGetTempFileName(Boolean checkHost) at System.Windows.Input.Cursor.LoadFromStream(Stream cursorStream) at System.Windows.Input.Cursor..ctor(Stream cursorStream) at Microsoft.VisualStudio.Text.Editor.Implementation.LeftSelectionMargin.get_RightArrowCursor() at Microsoft.VisualStudio.Text.Editor.Implementation.LeftSelectionMarginProvider.CreateMargin(IWpfTextViewHost textViewHost, IWpfTextViewMargin containerMargin) at Microsoft.VisualStudio.Text.Utilities.ContainerMargin.<AddMargins>b__2(IWpfTextViewMarginProvider mp) at Microsoft.VisualStudio.Text.Utilities.GuardedOperations.InstantiateExtension[TExtension,TMetadata,TExtensionInstance](Object errorSource, Lazy`2 provider, Func`2 getter)

I've disabled (not uninstalled though) every extension that I have.

I've searched multiple forums and most of those problems are code related. I can still compile and run, I just can't view the designer and every once in a while VS crashes. I've tried differentExpression tools also (i.e. Web, Blend). Web crashes, Blend doesn't start. Does anyone have any thoughts?

Edit 1: Something else that I have just noticed is that my gutters/line numbers are missing (Line Numbers IS enabled in options). Hmmm....

Edit 2: I'm getting the same error with Visual Studio 2010. This keeps getting better!

Edit 3: I've solved this issue (not sure if I can solve my own issue in this forum) so here it is.

Here is a quote from a site that I found (Keep reading after the quote):

======================================

If you get the System.IO.IOException: The file exists error, it’s probably because your C:/Windows/Temp folder is absolutely full with temporary files. In fact, if you have more than 65535 files in your temp folder, the method GetTempFileName will throw this error.

To resolve this, just remove all temporary files in C:/Windows/Temp. It might take some time, but it will solve the problem.

Here’s the stack trace I got:

System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   System.IO.Path.GetTempFileName()
======================================
The problem that I had was that my C:\Windows\Temp folder wasn't full. It was my AppData\Local\Temp folder! Once I cleared it I was good to go!