I worked a little on a development Rainbow site, rebuilt it, and tried to view it.  I got an error...

Configuration Error 
Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately. 

Parser Error Message: Access is denied: 'Esperantus'.

Source Error: 


Line 256:                <add assembly="System.EnterpriseServices, Version=1.0.5000.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"/>
Line 257:                <add assembly="System.Web.Mobile, Version=1.0.5000.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"/>
Line 258:                <add assembly="*"/>
Line 259:            </assemblies>
Line 260:

Source File: c:\winnt\microsoft.net\framework\v1.1.4322\Config\machine.config    Line: 258 

Assembly Load Trace: The following information can be helpful to determine why the assembly 'Esperantus' could not be loaded.

It took some time to find a link on MSDN that looked similar and recommended to turn off the Indexing Service. 

That worked, but why it was necessary now and not the 1,000 other times I've worked on this app., I don't know.