Sitecore Errors: fieldNameTranslator cannot be null

Symptoms:

1. Indexes complete instantly without actually rebuilding.
2. The content editor errors with the fieldNameTranslator cannot be null error.

This error typically comes up when Solr hasn't been configured correctly. The file global.asax needs to be changed from:

<%@Application Language='C#' Inherits="Sitecore.Web.Application" %>

to:

<%@ Application Language="C#" Inherits="Sitecore.ContentSearch.SolrProvider.CastleWindsorIntegration.WindsorApplication" %>