Why do I get the following error when executing a package under Business Intelligence Development Studio (BIDS)?

Why do I get the following error when executing a package under Business Intelligence Development Studio (BIDS)?

System.IO.FileNotFoundException: Could not load file or assembly 'Oracle.DataAccess, Version=2.111.6.20, Culture=neutral, PublicKeyToken=89b483f429c47342' or one of its dependencies. The system cannot find the file specified.

We have seen this error when using Oracle Data Provider for .NET 11.1.0.6.20 on 64bit OS. By default the SSIS project is setup to use the 64bit SSIS runtime for package debugging purposes. Set Run64BitRuntime project property to False to force SSIS to execute with the 32bit runtime.