Problem with Calendar Extender

I have the Calendar Extender from the Ajax Control Toolkit installed and running in Project1. I also want to use it in Project 2. I have added the same reference and the same markup code but in Project 2 I get this error.
Server Error in '/' Application. Could not find any resources appropriate for the specified culture or the neutral culture. Make sure "AjaxControlToolkit.Properties.Resources.NET4.resources" was correctly embedded or linked into assembly "AjaxControlToolkit" at compile time, or that all the satellite assemblies required are loadable and fully signed. 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.Resources.MissingManifestResourceException: Could not find any resources appropriate for the specified culture or the neutral cultur ...