Here is the code 

@using Examine;

@using Examine.LuceneEngine.SearchCriteria;

@using Examine.SearchCriteria;

@using UmbracoExamine;

@using System.Linq;

@using System.Xml.Linq;

@using umbraco.MacroEngines

@inherits umbraco.MacroEngines.DynamicNodeContext

@* Get the search term from query string *@

@{var searchTerm = Request.QueryString["q"];}

@{

   var Searcher = ExamineManager.Instance.SearchProviderCollection["InternalMemberIndexSet"];

   var searchCriteria = Searcher.CreateSearchCriteria(BooleanOperation.Or);

}

And The Config 

And it happens on Internal InternalMember and External Sets

Anyone. What more information do you need to assist me 

I just updated to 4.11.5 and had noticed that the examinIndex.config had changed... the internalindex now includes all fields not the subset as in previous releases//

could that be associated to your issue as I notice you have the prev limited index?

NEW

This configuration file can be extended to create your own index sets.
Index/Search providers can be defined in the UmbracoSettings.config

More information and documentation can be found on CodePlex: http://umbracoexamine.codeplex.com
-->
<ExamineLuceneIndexSets>
  <!-- The internal index set used by Umbraco back-office - DO NOT REMOVE -->
  <IndexSet SetName="InternalIndexSet" IndexPath="~/App_Data/TEMP/ExamineIndexes/Internal/"/>

  <!-- The internal index set used by Umbraco back-office for indexing members - DO NOT REMOVE -->
  <IndexSet SetName="InternalMemberIndexSet" IndexPath="~/App_Data/TEMP/ExamineIndexes/InternalMember/">
    <IndexAttributeFields>
      <add Name="id" />
      <add Name="nodeName"/>
      <add Name="updateDate" />
      <add Name="writerName" />
      <add Name="loginName" />
      <add Name="email" />
      <add Name="nodeTypeAlias" />
    </IndexAttributeFields>
  </IndexSet>

  <!-- Default Indexset for external searches, this indexes all fields on all types of nodes-->
  <IndexSet SetName="ExternalIndexSet" IndexPath="~/App_Data/TEMP/ExamineIndexes/External/" />
</ExamineLuceneIndexSets>

OLD

<?xml version="1.0"?>
<!-- 
Umbraco examine is an extensible indexer and search engine.
This configuration file can be extended to create your own index sets.
Index/Search providers can be defined in the UmbracoSettings.config

More information and documentation can be found on CodePlex: http://umbracoexamine.codeplex.com
-->
<ExamineLuceneIndexSets>
  <!-- The internal index set used by Umbraco back-office - DO NOT REMOVE -->
  <IndexSet SetName="InternalIndexSet" IndexPath="~/App_Data/TEMP/ExamineIndexes/Internal/">
    <IndexAttributeFields>
      <add Name="id" />
      <add Name="nodeName" />
      <add Name="updateDate" />
      <add Name="writerName" />
      <add Name="path" />
      <add Name="nodeTypeAlias" />
      <add Name="parentID" />
    </IndexAttributeFields>
    <IndexUserFields />
    <IncludeNodeTypes/>
    <ExcludeNodeTypes />
  </IndexSet>

  <!-- The internal index set used by Umbraco back-office for indexing members - DO NOT REMOVE -->
  <IndexSet SetName="InternalMemberIndexSet" IndexPath="~/App_Data/TEMP/ExamineIndexes/InternalMember/">
    <IndexAttributeFields>
      <add Name="id" />
      <add Name="nodeName"/>
      <add Name="updateDate" />
      <add Name="writerName" />
      <add Name="loginName" />
      <add Name="email" />
      <add Name="nodeTypeAlias" />
    </IndexAttributeFields>
    <IndexUserFields/>
    <IncludeNodeTypes/>
    <ExcludeNodeTypes />
  </IndexSet>

  <!-- Default Indexset for external searches, this indexes all fields on all types of nodes-->
  <IndexSet SetName="ExternalIndexSet" IndexPath="~/App_Data/TEMP/ExamineIndexes/External/" />
</ExamineLuceneIndexSets>

Thanks for your reply. No luck. I'm about to loose my mind. Cant see why this doesn't work

Trying a clean install of umbraco see if I can recreate the problem

Tried a clean install of umbraco 6 and I get the same error.

Anyone??

is working on a reply...