title: Server Error in '/' Application - An item with the same key has already been added
body: <p>I'm getting this error when the page loads. Not always happens, when I hit the refresh button the error is solved.</p>
  
  <p>An item with the same key has already been added.</p>
  
  <pre><code>Description: An unhandled exception occurred during the execution of the current web     request. Please review the stack trace for more information about the error and where it originated in the code. 
  
  Exception Details: System.ArgumentException: An item with the same key has already been added.
  
  Source Error: 
  
  An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
  
  Stack Trace: 
  
  
  [ArgumentException: An item with the same key has already been added.]
  System.ThrowHelper.ThrowArgumentException(ExceptionResource resource) +52
  System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)+9381419
  AjaxControlToolkit.ToolkitScriptManagerHelper.GetAssembly(String name) +52     AjaxControlToolkit.ToolkitScriptManagerCombiner.IsScriptCombinable(ScriptEntry scriptEntry,  Boolean enableCdn) +27
   AjaxControlToolkit.ToolkitScriptManagerCombiner.WriteScripts(List`1 scriptEntries, TextWriter outputWriter, Boolean enableCdn) + 122                   AjaxControlToolkit.ToolkitScriptManagerCombiner.GetCombinedRegisteredScriptContent(Boolean  enableCdn) +206
      AjaxControlToolkit.ToolkitScriptManagerCombiner.GetCombinedScriptContentHash(HttpContextBase context, String[] bundles, Boolean enableCdn) +18
  
  AjaxControlToolkit.ToolkitScriptManager.LoadScriptReferences(HttpContextBase context,    String[] bundles, Boolean forCombineAndMinify) +135
  
  AjaxControlToolkit.ToolkitScriptManager.OnLoad(EventArgs e) +215
  System.Web.UI.Control.LoadRecursive() +74
  System.Web.UI.Control.LoadRecursive() +146
  System.Web.UI.Control.LoadRecursive() +146
  System.Web.UI.Control.LoadRecursive() +146
  System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2207
  </code></pre>