Running SSIS on a 64-bit machine has several caveat that developers need to be aware of.  Tasks like the ActiveX task and Execute DTS 2000 Package Task only work either on a 32-bit machine or by running in 32-bit mode on a 64-bit machine.  This is also the case for many data providers like Excel, Access, and many ODBC drivers.  If you are working on a 64-bit machine don't worry there is a work around to keep yourself productive while still using 32-bit tasks and drivers.

Executing In BIDS

• Right-click on the project file and select properties in your solution
• Under the Debugging tab you will see a property called Run64BitRuntime which you need to change to true

Executing On Server

SQL Server 2008

• Either in a SQL Agent job or by just executing the package by itself there is a tab called Execution options. 
• Select Use 32 bit runtime and the package will then run in 32-bit mode

SQL Server 2005

• Use the 32-bit version of dtexec and execute your package from the command line which can be found in the Program Files (x86) folder.
• Follow link to execute package from command line http://msdn.microsoft.com/en-us/library/ms162810.aspx.