Page "locks" after attempt to edit page

1. Create a custom layout it my VS project (docs.sitefinity.com/feather-create-layout-files)

2. Re-build project - new layout shows up in SF

3. Create a page, specify the new layout, assign a widget to one of the place holders, edit widget, publish, view page - page shows with widget - so far, so good

4.  When I try an editing the page (I have tried un-publishing before editing  too)  in SF the page shows up but does not seems to load properly/completely - it just comes with the sprite image more like a static image (refer attached image)  and without the usual options for the widget "More" drop down.

5. The only way to get back is via the browser  back button - when I do that the page is locked.

In the error log I have the following:

Type : System.Web.HttpException, System.Web, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
Message : This is an invalid webresource request.
Source : System.Web
Help link : 
WebEventCode : 0
ErrorCode : -2147467259
Data : System.Collections.ListDictionaryInternal
TargetSite : Void System.Web.IHttpHandler.ProcessRequest(System.Web.HttpContext)
HResult : -2147467259
Stack Trace :    at System.Web.Handlers.AssemblyResourceLoader.System.Web.IHttpHandler.ProcessRequest(HttpContext context)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

Additional Info:

MachineName :<some name>
TimeStamp : 5/23/2016 9:12:25 PM
FullName : Telerik.Sitefinity.Utilities, Version=9.0.6010.0, Culture=neutral, PublicKeyToken=b28c218413bdf563
AppDomainName : 96616af7-2-131085106916424151
ThreadIdentity : admin
Requested URL : localhost:7037/.../WebResource.axd


Category: ErrorLog

Priority: 0

EventId: 90000

Severity: Error

Title:Enterprise Library Exception Handling

Machine: <some name>

App Domain: 96616af7-2-131085106916424151

ProcessId: 1340

Process Name: C:\Program Files (x86)\Telerik2\Sitefinity\Sitefinity.exe

Thread Name: 

Win32 ThreadId:2052

Extended Properties: 
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Hi,

As the article in question is related to Feather,  can you confirm on which type of page/page template this layout control is used - web-forms or MVC? 

Can you please provide  your layout control or isolated sample and the steps to reproduce the issue? Do you have the same behaviour when this layout is not used?

Regards,
Svetoslav Manchev
Telerik