I downloaded the new version of GCP and installed it, however, I didn't uninstall/delete the old GPC files/folders. Now I'm getting an Unhandled exception saying "The given key was not present in the directory." and WoW isn't launching from the Layout Editor. Here's the details from the exception:

See the end of this message for details on invoking
just-in-time (JIT) debugging instead of this dialog box.

************** Exception Text **************
System.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary.
at System.ThrowHelper.ThrowKeyNotFoundException()
at System.Collections.Generic.Dictionary`2.get_Item(TKey key)
at A.bc5e53a4dd83c48ce4fdd05ada6caece.983be5b7a1a1a1012e62f7e7ea434e34(Object , EventArgs )
at System.Windows.Forms.Control.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ButtonBase.WndProc(Message& m)
at System.Windows.Forms.Button.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

************** Loaded Assemblies **************
mscorlib
Assembly Version: 2.0.0.0
Win32 Version: 2.0.50727.4927 (NetFXspW7.050727-4900)
CodeBase: file:///C:/Windows/Microsoft.NET/Framework/v2.0.50727/mscorlib.dll
----------------------------------------
GCP_1
Assembly Version: 2.0.0.16
Win32 Version: 2.0.0.16
CodeBase: file:///C:/Users/Russ/AppData/Local/Temp/19597/GCP_1.exe
----------------------------------------
Microsoft.VisualBasic
Assembly Version: 8.0.0.0
Win32 Version: 8.0.50727.4927 (NetFXspW7.050727-4900)
CodeBase: file:///C:/Windows/assembly/GAC_MSIL/Microsoft.VisualBasic/8.0.0.0__b03f5f7f11d50a3a/Microsoft.VisualBasic.dll
----------------------------------------
System
Assembly Version: 2.0.0.0
Win32 Version: 2.0.50727.4927 (NetFXspW7.050727-4900)
CodeBase: file:///C:/Windows/assembly/GAC_MSIL/System/2.0.0.0__b77a5c561934e089/System.dll
----------------------------------------
System.Windows.Forms
Assembly Version: 2.0.0.0
Win32 Version: 2.0.50727.4927 (NetFXspW7.050727-4900)
CodeBase: file:///C:/Windows/assembly/GAC_MSIL/System.Windows.Forms/2.0.0.0__b77a5c561934e089/System.Windows.Forms.dll
----------------------------------------
System.Drawing
Assembly Version: 2.0.0.0
Win32 Version: 2.0.50727.4927 (NetFXspW7.050727-4900)
CodeBase: file:///C:/Windows/assembly/GAC_MSIL/System.Drawing/2.0.0.0__b03f5f7f11d50a3a/System.Drawing.dll
----------------------------------------
System.Runtime.Remoting
Assembly Version: 2.0.0.0
Win32 Version: 2.0.50727.4927 (NetFXspW7.050727-4900)
CodeBase: file:///C:/Windows/assembly/GAC_MSIL/System.Runtime.Remoting/2.0.0.0__b77a5c561934e089/System.Runtime.Remoting.dll
----------------------------------------
System.Configuration
Assembly Version: 2.0.0.0
Win32 Version: 2.0.50727.4927 (NetFXspW7.050727-4900)
CodeBase: file:///C:/Windows/assembly/GAC_MSIL/System.Configuration/2.0.0.0__b03f5f7f11d50a3a/System.Configuration.dll
----------------------------------------
System.Xml
Assembly Version: 2.0.0.0
Win32 Version: 2.0.50727.4927 (NetFXspW7.050727-4900)
CodeBase: file:///C:/Windows/assembly/GAC_MSIL/System.Xml/2.0.0.0__b77a5c561934e089/System.Xml.dll
----------------------------------------
ResourceAssembly
Assembly Version: 1.0.0.0
Win32 Version: 2.0.0.16
CodeBase: file:///C:/Users/Russ/AppData/Local/Temp/19597/GCP_1.exe
----------------------------------------
Microsoft.VisualBasic.Compatibility
Assembly Version: 8.0.0.0
Win32 Version: 8.0.50727.4927
CodeBase: file:///C:/Windows/assembly/GAC_MSIL/Microsoft.VisualBasic.Compatibility/8.0.0.0__b03f5f7f11d50a3a/Microsoft.VisualBasic.Compatibility.dll
----------------------------------------
Accessibility
Assembly Version: 2.0.0.0
Win32 Version: 2.0.50727.4927 (NetFXspW7.050727-4900)
CodeBase: file:///C:/Windows/assembly/GAC_MSIL/Accessibility/2.0.0.0__b03f5f7f11d50a3a/Accessibility.dll
----------------------------------------
Microsoft.mshtml
Assembly Version: 7.0.3300.0
Win32 Version: 7.0.3300.0
CodeBase: file:///C:/Windows/assembly/GAC/Microsoft.mshtml/7.0.3300.0__b03f5f7f11d50a3a/Microsoft.mshtml.dll
----------------------------------------
System.Core
Assembly Version: 3.5.0.0
Win32 Version: 3.5.30729.4926 built by: NetFXw7
CodeBase: file:///C:/Windows/assembly/GAC_MSIL/System.Core/3.5.0.0__b77a5c561934e089/System.Core.dll
----------------------------------------

************** JIT Debugging **************
To enable just-in-time (JIT) debugging, the .config file for this
application or computer (machine.config) must have the
jitDebugging value set in the system.windows.forms section.
The application must also be compiled with debugging
enabled.

For example:

<configuration>
<system.windows.forms jitDebugging="true" />
</configuration>

When JIT debugging is enabled, any unhandled exception
will be sent to the JIT debugger registered on the computer
rather than be handled by this dialog box.