Parser Error: Access is denied...

Problem

You get this error when attempting to run your application:

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: 'BaseClasses'.

This error is caused when the Microsoft Indexing Service on your system is currently indexing one of your application’s files.  Microsoft found a problem where files are getting locked and not released (in time).

Solution

Disable Microsoft Indexing Service and set it to manual so it does not auto-start again.  Alternatively, if you want to use the Indexing Service, then go to the Microsoft Management Console and expand "Services and Applications" then "Indexing Service" ->System ->Directories.  In the directories, you can explicitly add:

C:\WINNT\Microsoft.NET\Framework\ v1.1.4322\Temporary ASP.NET Files

...and set it NOT to be indexed.

Two possible resolutions are described in Microsoft knowledge base article 329065:

http://support.microsoft.com/default.aspx?scid=kb;en-us;329065

See Also

Part VII:  Troubleshooting Applications

Application Will Not Run

Application Runs But No Data is Displayed

Application Error Messages