If you’re using Crystal Reports 2008 in your ASP.NET application, and after deploying to a 64bit server getting following error:

An error has occurred while attempting to load the Crystal Reports runtime. Either the Crystal Reports registry key permissions are insufficient, or the Crystal Reports runtime is not installed correctly. Please install the appropriate Crystal Reports redistributable (CRRedist*.msi) containing the correct version of the Crystal Reports runtime (x86, x64, or Itanium) required. Please go to http://www.businessobjects.com/support for more information.

then switch your application to 32bit mode. In case of Windows 2003/IIS6 entire server will have to be switched, in case of Windows 2008/IIS7 a dedicated 32bit application pool can be established for your application.